I'm making an ASCII art game in c (windows), but for some reason when i play it is all flickering at apparently random intervals, and for most of the time i can't see anything. can anyone explain why or how to solve it?
this is my code:
const int WIDTH = 20, HEIGTH = 5;
const int AREA = (WIDTH) * HEIGTH;
const int gl = HEIGTH - 2; //Ground level
const float delta = 0.1f; //Frame rate
char scr[AREA]; //String for displaying stuff
char input;
int posx = 10, posy = gl - 1; //Player position
int vel = 0; //player velocity
while(1)
{
//TODO: player input
for(i = 0; i < AREA; i++) //Rendering part
{
if(i % WIDTH == 0 && i != 0)
{
scr[i] = '\n';
continue;
}
if(floor(i / WIDTH) >= gl) //i is on ground
{
scr[i] = '.';
continue;
}
scr[i] = ' ';
}
//Set player position
scr[posy * WIDTH + posx + 1] = '#';
scr[(posy + 1) * WIDTH + posx + 1] = '#';
system("cls");// Clear terminal
printf(scr);// Print screen
usleep(delta * 1000);//Sleep
}
output:
#
..........#........
...................►↓#
It works, but it flickers...
One possible reason for your problem is that there may be output waiting in the output buffer when you call your sleep function usleep. In that case, you should always flush all output before sleeping, by calling the function fflush( stdout );.
Also, using system("cls"); is highly inefficient. It is generally better to use the Console Functions API, or, if you are targetting platforms with Windows 10 or later, you can also use Console Virtual Terminal Sequences instead.
If you decide to use the Console Functions API, then the main functions that you will be needing in order to replace system("cls"); are GetStdHandle to obtain the output handle, and SetConsoleCursorPosition. That way, you won't have to clear the whole screen, but will only have to overwrite the parts of the screen that are changing. I also recommend that you replace printf with WriteConsole, otherwise you may run into buffering issues.
If this does not solve your flickering problem, then there also is the possibility of using double-buffering. Both the Console Functions API and Console Virtual Terminal Sequences support this.
When using the Console Functions API, you can use the function CreateConsoleScreenBuffer to create a new buffer to write to, without it being displayed immediately. This will allow you to first finish building the next screen, without any flickering occuring while doing so (because it is not being displayed yet). Once you have finished building the next screen, you can display it using the function SetConsoleActiveScreenBuffer.
Console Virtual Terminal Sequences offer similar functionality by supporting an alternate screen buffer.
Related
I would like to wrap a short text in a Text Box in Ncurses, but somehow my text keeps going off screen. How can I wrap the text so it (automatically) goes to a new line when reaching the end of the screen on the right?
I tried playing with '\n' and setting limits but witout results. Any tips what I am doing wrong? See below code for what is going on.
Thanks from a beginner programmer.
#include <ncurses.h>
#include <string.h>
void text(WINDOW* textborder, int wymax, int wxmax, char text5[], int size)
{
for (int i=0;i<size;i++)
{
mvwaddch(textborder,2,i+i, text5[i]);
if (i==wxmax)
{
mvwaddch(textborder,2,i+i, '\n');
}
}
}
int main()
{
char text5[]={"Somebody is watching over us... controlling us. It's true, I tell you. It's true! We are merely sprites that dance at the beck and call of our button-pressing overlord. This is a video game. Don't you see? We are characters in a video game."};
int size;
size=strlen(text5);
int wymax; int wxmax;
initscr();
WINDOW* textborder=newwin(LINES/4, COLS, LINES-LINES/4, 0);
box(textborder,-1,-1);
getmaxyx(textborder, wymax,wxmax);
wxmax=wxmax-4;
text(textborder, wymax, wxmax, text5, size);
wgetch(textborder);
endwin();
return 0;
}
In theory the text should wrap itself. I think your issue may be coming from using mvwaddch, ch generally causes the text not to wrap. This may help Ncurses no-wrap mode when adding strings to window. Sorry I can't be more helpful :)
Applications that draw a box with a border in curses do this using two windows, one within the other. The outer box gets the border; the inner box gets the text. Text printed within the inner box does not affect the outer box.
For example, some of the demo/example programs in ncurses do this, e.g., test_addstr creates look (for the box) and show (for the text):
limit = LINES - 5;
if (level > 0) {
look = newwin(limit, COLS - (2 * (level - 1)), 0, level - 1);
work = newwin(limit - 2, COLS - (2 * level), 1, level);
show = newwin(4, COLS, limit + 1, 0);
box(look, 0, 0);
wnoutrefresh(look);
limit -= 2;
} else {
work = stdscr;
show = derwin(stdscr, 4, COLS, limit + 1, 0);
}
keypad(work, TRUE);
I am making a game in CSFML for the purpose of a school exercise
In order to fit all the requirement I must a game who follows the rule of a finite runne suc as geometry dash. It does everything except a major feature: get a map from a file that will be like:
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
XXXXXXXXXX2XXXXXXXXX2XXXXXXXXXXXXXXE
111111111111111111111111111111111111
X representing nothing (they will be a background that is displayed)
2 is spike
1 is the ground
E is the end, it will stop the program after displaying a victory screen
(each character will be replace by the texture who is assigned except X who represent empty space)
I had only access to few C functions ( write, free, malloc, rand, open, read,getline)
I was thinking about just reading the file and storing it as a char*, but the thing is I don't know how to make spikes appear on the screen one by one, when they must.
You need to choose a size for all of your blocks.
Each blocks (X, 2, 1, E) need to have the same size.
Example (with block 64*64px)
void display_map(char **map)
{
char *image = NULL;
int size_block = 64;
for (int i = 0; map[i] != NULL; i++) {
for (int j = 0; map[i][j] != '\0'; j++) {
switch (map[i][j]) {
case 'X':
image = "nothing";
break;
case '2':
image = "pike";
break;
// ....
}
display_at_position(i * size_block, j * size_block, image);
}
}
}
I work in Code Composer Studio Version: 6.0.1.00040
with the card LCDK C6748, but I think this is a more general question, relating to CCS generally.
I'm trying to implement LMS for cancelling acoustic echoes,
this is the skeleton of my .c file:
void waitForInterrupt()
{
while (flag==0) {}
flag=0; // reach this line only when flag == 1
}
interrupt void interrupt4(void)
{
// Inputs
inputRight_micSignal = (float)input_right_sample();
// Outputs
outputLeft_referenceSignal= whiteNoiseSample;
codec_data.channel[RIGHT]= (uint16_t)outputRight_cleanedSound;
codec_data.channel[LEFT]= (uint16_t)outputLeft_referenceSignal;
output_sample(codec_data.uint);
flag = 1;
}
void main()
{
// variables decelerations
int i;
float filter_output;
// initialising filter coefficients
for (i=0 ; i<ADAPTIVE_FILT_SIZE ; i++) // initialise weights and delay line
{
w[i] = 0.0;
x[i] = 0.0;
}
// initialising the interrupt routine
L138_initialise_intr(FS_8000_HZ,ADC_GAIN_0DB,DAC_ATTEN_0DB,LCDK_MIC_INPUT);
while(1) // adaptive filtering routine
{
waitForInterrupt();
whiteNoiseSample = getPrnFiltered();
for (i = ADAPTIVE_FILT_SIZE-1; i > 0; i--) // update delay line - TDL:merge later with w loop (still make sure no magic NaN's appear)
{
x[i] = x[i-1];
}
x[0] = outputLeft_referenceSignal; // input to adaptive filter
filter_output = 0; //reseting filter output
// compute adaptive filter output
for (i = 0; i < ADAPTIVE_FILT_SIZE; i++)
filter_output += (w[i]*x[i]);
outputRight_cleanedSound = inputRight_micSignal - filter_output; // compute error
for (i = ADAPTIVE_FILT_SIZE-1; i >= 0; i--) // update weights and delay line
{
w[i] = w[i] + beta*outputRight_cleanedSound*x[i]; // w[i]+=beta*"error"*"reference"
}
from some reason when I put the arrays x[] and w[] in the "watch table"
and I suspend the running of the program (in order to examine w[] coefficients after awhile, I see that it is full of NaN's - while x[] contains "regular"
values.
when I put breakpoint inside the line where w[] is calculated:
w[i] = w[i] + beta*outputRight_cleanedSound*x[i]; // w[i]+=beta*"error"*"reference"
I see the flow goes there.
What could be the reason for the NaN's?
Is there a way to watch w[] in the "wach table"?
These three steps work for me:
1) First you need to make sure the variables are globally available (e.g. that they are not allocated on the stack).
2) You need to halt the processor before trying to read the variables. (In Debug view: Tools -> Debugger Options -> Auto Run and Launch Options).
3) Enable "halt the target before any debugger access" on the watch window and click the "auto-update" icon in the "Variables"-window.
I've uploaded a screenshot with red boxes around the stuff you need to touch.
See if that helps you :) Otherwise check out TI's Engineer2Engineer forum (E2E). In my experience the TI guys are quick to answer and I've gotten very competent help from them.
Tell me how it works for you :) ?
FWIW I'm using Code Composer Studio v.5.5.0.00077.
I'm working a simple candy crush game for my year 1 assignment.
I am at this stage where I need to show my self-made simple marker( *box made of '|' and '_'* ) on the center of the board ( board[5][5] ) once the program is executed.
Here is the current code:
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
//FUNCTION: Draw the Board
int drawBoard()
{
//Declare array size
int board[9][9];
//initialize variables
int rows, columns, randomNumber, flag;
//random number seed generator
srand(time(NULL));
for ( rows = 0 ; rows < 9 ; rows++ )
{
for ( columns = 0 ; columns < 9 ; columns++ )
{
flag = 0;
do
{
//generate random numbers from 2 - 8
randomNumber = rand() %7 + 2;
board[rows][columns] = randomNumber;
//Checks for 2 adjacent numbers.
if ( board[rows][columns] == board[rows - 1][columns] || board[rows][columns] == board[rows][columns - 1] )
{
flag = 0;
continue;
}
else
{
flag = 1;
printf( " %d ", board[rows][columns] );
}
} while ( flag == 0 );
}//end inner for-loop
printf("\n\n");
}//end outer for-loop
//call FUNCTION marker() to display marker around board[5][5]
marker( board[5][5] );
}//end FUNCTION drawBoard
//FUNCTION: Mark the surrounding of the number with "|" and "_" at board[5][5]
void marker( int a )
{
printf( " _ \n" );
printf( "|%c|\n", a );
printf( " _ \n" );
}
int main()
{
drawBoard();
}
At the end of function drawBoard(), I placed the code marker( board[5][5] ).
This should have printed the markers around the number printed at coordinate board[5][5]..but for some reason it displays right after the board has been printed.
So why doesn't it print at that coordinate although I specified it at board[5][5]?
What could be the problem here?
so in your marker function you need to pass the board and the coordinate you want to print at
void marker( int x, int y, int** board )
{
board[x][y-1]="_";
board[x-1][y]="|";
board[x+1][y]="|";
board[x][y+1]="_";
}
then after the call to marker(5,5,board), call drawboard again
my code's a bit off but that's the logic, except you need to check for the case that the marker is at the edge of the board
in other words, you need to keep board around, and any time you make a change to it, clear the screen and print the whole board out again.
There is no persistent drawing in the way that you are doing this. You are just printing straight to the shell/command prompt. The way that you trying to do things will not work. You can't edit something drawn to the prompt after you have drawn it, you need to basically clear the screen and then draw again but with your indicated maker.
I don't know if you are able to use libraries in your assignment, but a very good library that WILL let you do is ncurses
EDIT Full rewrite of answer
Drawing Things On Top of One Another In CMD
Alright, I had some downtime at work, so I wrote a project to do what you need and I'm going to post code and explain what it does and why you need it along the way.
First thin that you are going to need a basically a render buffer or a render context. Whenever you are programming in a graphics API such as OpenGL, you don't just render straight to the screen, you render each object that you have to a buffer that rasterizes your content and turns it into pixels. Once it's in that form, the API shoves the rendered picture onto the screen. We are going to take a similar approach where instead of drawing to a pixel buffer on the GPU, we are going to draw to a character buffer. Think about each character as a pixel on the screen.
Here is a pastebin of the complete source:
Complete Source of Project
RenderContext
Our class to do this will be the RenderContext class. It has fields to hold width and height as well as an array of chars and a special char that we fill our buffer with whenever we clear it.
This class simply holds an array and functions to let us render to it. It makes sure that when we draw to it, we are within bounds. It is possible for an object to try to draw outside of the clipping space (off screen). However, whatever is drawn there is discarded.
class RenderContext {
private:
int m_width, m_height; // Width and Height of this canvas
char* m_renderBuffer; // Array to hold "pixels" of canvas
char m_clearChar; // What to clear the array to
public:
RenderContext() : m_width(50), m_height(20), m_clearChar(' ') {
m_renderBuffer = new char[m_width * m_height];
}
RenderContext(int width, int height) : m_width(width), m_height(height), m_clearChar(' ') {
m_renderBuffer = new char[m_width * m_height];
}
~RenderContext();
char getContentAt(int x, int y);
void setContentAt(int x, int y, char val);
void setClearChar(char clearChar);
void render();
void clear();
};
The two most important functions of this class are setContentAt and render
setContentAt is what an object calls to fill in a "pixel" value. To make this a little more flexible, our class uses a pointer to an array of chars rather than a straight array (or even a two dimensional array). This lets us set the size of our canvas at runtime. Because of this, we access elements of this array with x + (y * m_width) which replaces a two dimensional dereference such as arr[i][j]
// Fill a specific "pixel" on the canvas
void RenderContext::setContentAt(int x, int y, char val) {
if (((0 <= x) && (x < m_width)) && ((0 <= y) && (y < m_height))) {
m_renderBuffer[(x + (y * m_width))] = val;
}
}
render is what actually draws to the prompt. All it does is iterate over all the "pixels" in it's buffer and place them on screen and then moves to the next line.
// Paint the canvas to the shell
void RenderContext::render() {
int row, column;
for (row = 0; row < m_height; row++) {
for (column = 0; column < m_width; column++) {
printf("%c", getContentAt(column, row));
}
printf("\n");
}
}
I_Drawable
Our next class is an Interface that lets us contract with objects that they can draw to our RenderContext. It is pure virtual because we don't want to actually be able to instantiate it, we only want to derive from it. It's only function is draw which accepts a RenderContext. Derived classes use this call to receive the RenderContext and then use RenderContext's setContentAt to put "pixels" into the buffer.
class I_Drawable {
public:
virtual void draw(RenderContext&) = 0;
};
GameBoard
The first class to implement the I_Drawable, thus being able to render to our RenderContext, is the GameBoard class. This is where a majority of the logic comes in. It has fields for width, height, and a integer array that holds the values of the elements on the board. It also has two other fields for spacing. Since when you draw your board using your code, you have spaces between each element. We don't need to incorporate this into the underlying structure of the board, we just need to use them when we draw.
class GameBoard : public I_Drawable {
private:
int m_width, m_height; // Width and height of the board
int m_verticalSpacing, m_horizontalSpacing; // Spaces between each element on the board
Marker m_marker; // The cursor that will draw on this board
int* m_board; // Array of elements on this board
void setAtPos(int x, int y, int val);
void generateBoard();
public:
GameBoard() : m_width(10), m_height(10), m_verticalSpacing(5), m_horizontalSpacing(3), m_marker(Marker()) {
m_board = new int[m_width * m_height];
generateBoard();
}
GameBoard(int width, int height) : m_width(width), m_height(height), m_verticalSpacing(5), m_horizontalSpacing(3), m_marker(Marker()) {
m_board = new int[m_width * m_height];
generateBoard();
}
~GameBoard();
int getAtPos(int x, int y);
void draw(RenderContext& renderTarget);
void handleInput(MoveDirection moveDirection);
int getWidth();
int getHeight();
};
It's key functions are generateBoard, handleInput, and the derived virtual function draw. However, do note that in its constructor it creates a new int array and gives it to its pointer. Then its destructor automatically removes the allocated memory whenever the board goes away.
generateBoard is what we use to actual create the board and fill it with numbers. It will iterate over each location on the board. Each time, it will look at the elements directly to the left and above and store them. Then it will generate a random number until the number it generates does not match either of the stored elements, then it stores the number in the array. I rewrote this to get rid of the flag usage. This function gets called during the construction of the class.
// Actually create the board
void GameBoard::generateBoard() {
int row, column, randomNumber, valToLeft, valToTop;
// Iterate over all rows and columns
for (row = 0; row < m_height; row++) {
for (column = 0; column < m_width; column++) {
// Get the previous elements
valToLeft = getAtPos(column - 1, row);
valToTop = getAtPos(column, row - 1);
// Generate random numbers until we have one
// that is not the same as an adjacent element
do {
randomNumber = (2 + (rand() % 7));
} while ((valToLeft == randomNumber) || (valToTop == randomNumber));
setAtPos(column, row, randomNumber);
}
}
}
handleInput is what deals with moving the cursor around on the board. It's basically a freebie and your next step after getting the cursor to draw over the board. I needed a way to test the drawing. It accepts an enumeration that we switch on to know where to move our cursor to next. If you maybe wanted to have your cursor wrap around the board whenever you reach an edge, you would want to do that here.
void GameBoard::handleInput(MoveDirection moveDirection) {
switch (moveDirection) {
case MD_UP:
if (m_marker.getYPos() > 0)
m_marker.setYPos(m_marker.getYPos() - 1);
break;
case MD_DOWN:
if (m_marker.getYPos() < m_height - 1)
m_marker.setYPos(m_marker.getYPos() + 1);
break;
case MD_LEFT:
if (m_marker.getXPos() > 0)
m_marker.setXPos(m_marker.getXPos() - 1);
break;
case MD_RIGHT:
if (m_marker.getXPos() < m_width - 1)
m_marker.setXPos(m_marker.getXPos() + 1);
break;
}
}
draw is very important because it's what gets the numbers into the RenderContext. To summarize, it iterates over every element on the board, and draws in the correct location on the canvas placing an element under the correct "pixel". This is where we incorporate the spacing. Also, take care and note that we render the cursor in this function.
It's a matter of choice, but you can either store a marker outside of the GameBoard class and render it yourself in the main loop (this would be a good choice because it loosens the coupling between the GameBoard class and the Marker class. However, since they are fairly coupled, I chose to let GameBoard render it. If we used a scene graph, as we probably would with a more complex scene/game, the Marker would probably be a child node of the GameBoard so it would be similar to this implementation but still more generic by not storing an explicit Marker in the GameBoard class.
// Function to draw to the canvas
void GameBoard::draw(RenderContext& renderTarget) {
int row, column;
char buffer[8];
// Iterate over every element
for (row = 0; row < m_height; row++) {
for (column = 0; column < m_width; column++) {
// Convert the integer to a char
sprintf(buffer, "%d", getAtPos(column, row));
// Set the canvas "pixel" to the char at the
// desired position including the padding
renderTarget.setContentAt(
((column * m_verticalSpacing) + 1),
((row * m_horizontalSpacing) + 1),
buffer[0]);
}
}
// Draw the marker
m_marker.draw(renderTarget);
}
Marker
Speaking of the Marker class, let's look at that now. The Marker class is actually very similar to the GameBoard class. However, it lacks a lot of the logic that GameBoard has since it doesn't need to worry about a bunch of elements on the board. The important thing is the draw function.
class Marker : public I_Drawable {
private:
int m_xPos, m_yPos; // Position of cursor
public:
Marker() : m_xPos(0), m_yPos(0) {
}
Marker(int xPos, int yPos) : m_xPos(xPos), m_yPos(yPos) {
}
void draw(RenderContext& renderTarget);
int getXPos();
int getYPos();
void setXPos(int xPos);
void setYPos(int yPos);
};
draw simply puts four symbols onto the RenderContext to outline the selected element on the board. Take note that Marker has no clue about the GameBoard class. It has no reference to it, it doesn't know how large it is, or what elements it holds. You should note though, that I got lazy and didn't take out the hard coded offsets that sort of depend on the padding that the GameBoard has. You should implement a better solution to this because if you change the padding in the GameBoard class, your cursor will be off.
Besides that, whenever the symbols get drawn, they overwrite whatever is in the ContextBuffer. This is important because the main point of your question was how to draw the cursor on top of the GameBoard. This also goes to the importance of draw order. Let's say that whenever we draw our GameBoard, we drew a '=' between each element. If we drew the cursor first and then the board, the GameBoard would draw over the cursor making it invisible.
If this were a more complex scene, we might have to do something fancy like use a depth buffer that would record the z-index of an element. Then whenever we drew, we would check and see if the z-index of the new element was closer or further away than whatever was already in the RenderContext's buffer. Depending on that, we might skip drawing the "pixel" altogether.
We don't though, so take care to order your draw calls!
// Draw the cursor to the canvas
void Marker::draw(RenderContext& renderTarget) {
// Adjust marker by board spacing
// (This is kind of a hack and should be changed)
int tmpX, tmpY;
tmpX = ((m_xPos * 5) + 1);
tmpY = ((m_yPos * 3) + 1);
// Set surrounding elements
renderTarget.setContentAt(tmpX - 0, tmpY - 1, '-');
renderTarget.setContentAt(tmpX - 1, tmpY - 0, '|');
renderTarget.setContentAt(tmpX - 0, tmpY + 1, '-');
renderTarget.setContentAt(tmpX + 1, tmpY - 0, '|');
}
CmdPromptHelper
The last class that I'm going to talk about is the CmdPromptHelper. You don't have anything like this in your original question. However, you will need to worry about it soon. This class is also only useful on Windows so if you are on linux/unix, you will need to worry about dealing with drawing to the shell yourself.
class CmdPromptHelper {
private:
DWORD inMode; // Attributes of std::in before we change them
DWORD outMode; // Attributes of std::out before we change them
HANDLE hstdin; // Handle to std::in
HANDLE hstdout; // Handle to std::out
public:
CmdPromptHelper();
void reset();
WORD getKeyPress();
void clearScreen();
};
Each one of the functions is important. The constructor gets handles to the std::in and std::out of the current command prompt. The getKeyPress function returns what key the user presses down (key-up events are ignored). And the clearScreen function clears the prompt (not really, it actually moves whatever is already in the prompt up).
getKeyPress just makes sure you have a handle and then reads what has been typed into the console. It makes sure that whatever it is, it is a key and that it is being pressed down. Then it returns the key code as a Windows specific enum usually prefaced by VK_.
// See what key is pressed by the user and return it
WORD CmdPromptHelper::getKeyPress() {
if (hstdin != INVALID_HANDLE_VALUE) {
DWORD count;
INPUT_RECORD inrec;
// Get Key Press
ReadConsoleInput(hstdin, &inrec, 1, &count);
// Return key only if it is key down
if (inrec.Event.KeyEvent.bKeyDown) {
return inrec.Event.KeyEvent.wVirtualKeyCode;
} else {
return 0;
}
// Flush input
FlushConsoleInputBuffer(hstdin);
} else {
return 0;
}
}
clearScreen is a little deceiving. You would think that it clears out the text in the prompt. As far as I know, it doesn't. I'm pretty sure it actually shifts all the content up and then writes a ton of characters to the prompt to make it look like the screen was cleared.
An important concept that this function brings up though is the idea of buffered rendering. Again, if this were a more robust system, we would want to implement the concept of double buffering which means rendering to an invisible buffer and waiting until all drawing is finished and then swap the invisible buffer with the visible one. This makes for a much cleaner view of the render because we don't see things while they are still getting drawn. The way we do things here, we see the rendering process happen right in front of us. It's not a major concern, it just looks ugly sometimes.
// Flood the console with empty space so that we can
// simulate single buffering (I have no idea how to double buffer this)
void CmdPromptHelper::clearScreen() {
if (hstdout != INVALID_HANDLE_VALUE) {
CONSOLE_SCREEN_BUFFER_INFO csbi;
DWORD cellCount; // How many cells to paint
DWORD count; // How many we painted
COORD homeCoord = {0, 0}; // Where to put the cursor to clear
// Get console info
if (!GetConsoleScreenBufferInfo(hstdout, &csbi)) {
return;
}
// Get cell count
cellCount = csbi.dwSize.X * csbi.dwSize.Y;
// Fill the screen with spaces
FillConsoleOutputCharacter(
hstdout,
(TCHAR) ' ',
cellCount,
homeCoord,
&count
);
// Set cursor position
SetConsoleCursorPosition(hstdout, homeCoord);
}
}
main
The very last thing that you need to worry about is how to use all these things. That's where main comes in. You need a game loop. Game loops are probably the most important thing in any game. Any game that you look at will have a game loop.
The idea is:
Show something on screen
Read input
Handle the input
GOTO 1
This program is no different. The first thing it does is create a GameBoard and a RenderContext. It also makes a CmdPromptHelper which lets of interface with the command prompt. After that, it starts the loop and lets the loop continue until we hit the exit condition (for us that's pressing escape). We could have a separate class or function do dispatch input, but since we just dispatch the input to another input handler, I kept it in the main loop. After you get the input, you send if off to the GameBoard which alters itself accordingly. The next step is to clear the RenderContext and the screen/prompt. Then rerun the loop if escape wasn't pressed.
int main() {
WORD key;
GameBoard gb(5, 5);
RenderContext rc(25, 15);
CmdPromptHelper cph;
do {
gb.draw(rc);
rc.render();
key = cph.getKeyPress();
switch (key) {
case VK_UP:
gb.handleInput(MD_UP);
break;
case VK_DOWN:
gb.handleInput(MD_DOWN);
break;
case VK_LEFT:
gb.handleInput(MD_LEFT);
break;
case VK_RIGHT:
gb.handleInput(MD_RIGHT);
break;
}
rc.clear();
cph.clearScreen();
} while (key != VK_ESCAPE);
}
After you have taken into consideration all of these things, you understand why and where you need to be drawing your cursor. It's not a matter of calling a function after another, you need to composite your draws. You can't just draw the GameBoard and then draw the Marker. At least not with the command prompt. I hope this helps. It definitely alleviated the down time at work.
Window bottom
Some applications like vim, mutt, aptitude contain
a top window section for output and
a bottom section for the user to type in or for status display.
(Suppose there is one child process to output and another one to take user input. The purpose is to allow for updated output at the same time as you are typing the input or viewing the status.)
Actions Undo Package Resolver Search Options Views Help
C-T: Menu ?: Help q: Quit u: Update g: Download/Install/Remove Pkgs
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┌─────────────┐ |
│Loading cache│ |
└─────────────┘ |
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--------------------------------------------------------------------------- |
Initialising package states 100% |
+-------------------------------------------------------+
| some output here |
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|-------------------------------------------------------+
|:input here |
+-------------------------------------------------------+
Ncurses tutorial does not mention this to be obviously possible.
A query on "c print to {window,screen,terminal,console} bottom" at StackOverflow or at a web search engine isn't helpful.
Can this be done in C programmatically?
Discarding input
While some of the solutions below can move character to a given position, there is the problem that it may be needed to discard user input rather than leaving it on screen. Like in vim's case, typing ":w" and pressing Enter does not leave a ":w" on the screen.
Update. This is found here: How to delete text after getstr() c++ ncurses
Window focus - the UNSOLVED PART OF THE PROBLEM
While you are typing the input at window bottom and the text at the top changes, we see the problem of moving the focus back to the bottom. This is absent in the solutions as of December 29.
Update 1. Just attempting to
remember the previous cursor position, then
display the output, and then
restore the position
is not an easy solution: as these are different processes, attempts to retrieve cursor position don't affect the changes that happened during the other process execution.
Eg if parent takes input then the child doesn't know how the cursor position changed and can't restore the cursor position after performing a line of output at another part of the console.
Implementing this would involve some inter process communication and if there are other solutions they could be preferable.
Related
Get Input from keyboard without waiting for input Related, but not specific enough.
How to make a chat like UI using Python Urwid? Urwid for Python which does the job (per J.F. Sebastian in the comment below). Unfortunately not in C.
Using the standard libraries, there's no way to do that; using ncurses, as you already suggest, it is easily possible; I think this tutorial explains it quite nicely.
Using ANSI escape sequence it's possible to control the position of the cursor:
void gotoxy(int x, int y) {
printf("\033[%d;%dH",x,y);
}
So once you figure out the terminal height and width then you can use that function to position the cursor wherever you like and print stuff.
This answer suggests a slightly different approach, but it avoids a lot of complication you'd introduce by using the current method. I hope it is possible to implement these simplifications.
Use termio to turn off canonical mode.
Sample code (here) will show you exactly how to set up such an input loop. This sample 'polls-and-sleeps' which could mean a delay unless you reduce the sleep. Also I think you can use termio to set a timeout (wait a second and return 'no input' or give me the input NOW if it comes earlier). But if you are really going to monitor another process, polling might be the more flexible option.. You can really poll 30x a second and live with the .00001% processor hit it is going to cause, but you will love the simplicity and bug prevention it gives.
Avoid multiple threads and processes like the plague
You don't need to use 2 processes/threads if the only problem you are trying to solve is the fact that getch() blocks. That would be required if it were impossible to prevent the input functions from blocking. 'Canonical' (rules based) means all sorts of handy 'rules' are in effect, like, 'don't give the input to the program until ENTER is hit'. For a full screen console app you want to turn off all the rules and do everything yourself.
Put the main thread in charge of the window...
... Then you can just use the ansi escape csi codes to position the cursor back to where you want it. Caveat: you can't write to the lower-right box in the screen. Everything will scroll.
There is an annoying thing in MS windows programming where only the thread that creates a window can safely update it. There is actually a reason for this. Whether you're talking console, or windowing system. sooner or later, if you have multiple threads/processing hitting one output device, you'll interrupt an escape sequence (or have to make extra code to manage this which is a bad thing), be fighting for the output 'port', etc. you need one thread to manage the output.
if you really care about what some other thread or process is doing, just check it in your main console management loop. For example of you have another process that you just want to report its progress, start it from your program and capture its stdouput and look at that; another thread, just lock something shared you can check in your polling routine. Heck if it's just a byte and it's only used for statuses, don't even lock the damn thing. You can throw in a couple of GOTO's too, just to show your individuality :-)
caveat I don't know that ncurses would play well with you if you are manually messing with termio? I would guess it wants to do that itself. Never tried mixing. If your app is simple you could go it alone without the help, especially if you can wrestle ncurses into doing what you want. I'm no expert on those apps you mention but I'd bet they are micromanaging everything.
I had a similar issue a few weeks ago while writing an IRC client that runs in the terminal. I wrote it using the Windows conio library, but I'm fairly sure this should be applicable to curses. The idea is that console output is handled by a single thread, and console input is handled in a separate thread. Basically, all you need is a loop that pushes the return of getch() onto a mutexed FIFO that runs for the duration of the program. In the display thread, you can pop the keypresses off the FIFO and handle them however you like. You can't use a standard function like fgets(), but it's a very solid solution to your problem. I can provide the full (messy) source on request.
Edit: alright, well here's the relevant code from the FIFO pushing:
bool keyqueuewriting = false;
std::deque<int> keyqueue;
void grabkey( void* in )
{
int t;
while( true ){
t = getch();
#ifdef _WIN32
if( t == 224 || t == 0 )
{
t += getch() << 8;
}
#else
int off = 8;
if( t == 27 ){
int e = getch();
t += e << off;
off += 8;
while( e ==91 || (e >= '0' && e <= '9') || e == ';' )
{
e = getch();
t += e << off;
off += 8;
}
}
#endif
while( keyqueuewriting ){}
keyqueuewriting = true;
keyqueue.push_back( t );
keyqueuewriting = false;
}
}
And Handling:
while( keyqueuewriting ){}
keyqueuewriting = true;
while( keyqueue.size() > 0 )
{
shouldsleep = false;
int t = keyqueue.front();
keyqueue.pop_front();
switch( t )
{
case K_BACKSPACE:
if( pos > 0 ){
for( int i = pos-1; input[i] != 0; i++ ){input[i] = input[i+1];}
movecursorback( 1 );
pos -= 1;
} break;
case K_LEFT: if( pos > 0 ){ movecursorback( 1 ); pos -= 1; } break;
case K_RIGHT: if( input[pos] != 0 ) {movecursorforward( 1 ); pos += 1;} break;
case K_HOME: { gotoxy(0,SCREENHIG-1); pos = 0; } break;
case K_END: { int a = strlen( input ); /*gotoxy( 79,39 );*/ pos = a;} break;
case 3: exit(3); break;
default: if( t >= 0x20 && t < 0x80 ){
int a = strlen( input );
if( a > 998 )
a = 998;
int deadcode = 1;
input[999] = 0;
for( int i = a+1; i > pos; i-- ){input[i] = input[i-1];}
input[ pos ] = t;
movecursorforward( 1 );
pos++;
} break;
}
change = bufpos[curroom] - bufprev;
if( pos > 998 ) pos = 998;
if( pos - mescroll < 1 ) {mescroll += (pos-mescroll-1); gotoxy( pos-mescroll, SCREENHIG-1 );}
if( pos - mescroll > 78 ) {mescroll += (pos-mescroll-78); gotoxy( pos-mescroll, SCREENHIG-1 );}
if( mescroll < 0 ) {mescroll = 0; gotoxy( 0, SCREENHIG-1 ); }
savexy();
gotoxy( 0, SCREENHIG-1 );
char y = (input+mescroll)[79];
(input+mescroll)[79] = 0;
printf( "%s ", input+mescroll );
(input+mescroll)[79] = y;
returntosaved();
change2 = change;
bufprev = bufpos[curroom];
}
keyqueuewriting = false;
Yes, it uses std::deque. That should be the only C++ specific thing though. Just replace it with a C compatible FIFO.
The entire client can be found here.
Yes, it DOES compile in Linux, but it doesn't work. I never bothered to figure out how ncurses should be used before I started work on it.