Rendering in a small section of my window - c

Question

I am currently working with SDL2. I am on Mac OS and I'm using xCode.
I have created a function to draw lines using randomly generated points.
However, when I try to render the lines, they are only render in a subset of my window (top left square).
Here's my code.
main.c
#include <SDL2/SDL.h>
#include "utils.h"
#define SCREEN_WIDTH 640
#define SCREEN_HEIGHT 480
// Prototypes
void drawRandomPoints( int pointsNo, SDL_Renderer *renderer );
void drawRandomLines( int linesNo, SDL_Renderer *renderer );
int main( int argc, const char * argv[] ) {
SDL_Init( SDL_INIT_VIDEO );
SDL_Window *window = SDL_CreateWindow( "Hello World", SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED, SCREEN_WIDTH, SCREEN_HEIGHT, SDL_WINDOW_ALLOW_HIGHDPI | SDL_WINDOW_OPENGL );
SDL_Renderer *renderer = SDL_CreateRenderer( window, -1, SDL_RENDERER_ACCELERATED | SDL_RENDERER_PRESENTVSYNC );
int running = 1;
SDL_Event event;
while( running ) {
while( SDL_PollEvent( &event ) ) {
if( event.type == SDL_QUIT ) {
running = 0;
}
}
SDL_SetRenderDrawColor( renderer, 0, 0, 0, 255 );
SDL_RenderClear( renderer );
// Draw a point
SDL_SetRenderDrawColor( renderer, 255, 0, 0, 255 );
drawRandomLines( 100, renderer );
SDL_RenderPresent( renderer );
}
SDL_DestroyRenderer( renderer );
SDL_DestroyWindow( window );
SDL_Quit();
return 0;
}
void drawRandomPoints( int pointsNo, SDL_Renderer *renderer ) {
int i = 0;
for( i = 0; i < pointsNo; ++i ) {
SDL_SetRenderDrawColor( renderer, getRandomColor(), getRandomColor(), getRandomColor(), 255 );
SDL_RenderDrawPoint( renderer, getRandomNumber( 0, SCREEN_WIDTH ), getRandomNumber( 0, SCREEN_HEIGHT ) );
}
}
void drawRandomLines( int linesNo, SDL_Renderer *renderer ) {
int i = 0;
for( i = 0; i < linesNo; ++i ) {
SDL_SetRenderDrawColor( renderer, getRandomColor(), getRandomColor(), getRandomColor(), 255 );
SDL_RenderDrawLine( renderer, getRandomNumber( 0, SCREEN_WIDTH ), getRandomNumber( 0, SCREEN_HEIGHT ), getRandomNumber( 0, SCREEN_WIDTH ), getRandomNumber( 0, SCREEN_HEIGHT ) );
}
}
utils.c
#include "utils.h"
#include <stdlib.h>
#include <time.h>
int getRandomNumber( int min, int max ) {
static int init = 0;
if( !init ) {
srand( time( NULL ) );
init = 1;
}
return ( rand() % ( max - min + 1 ) ) + min;
}
int getRandomColor() {
return getRandomNumber( 0, 255 );
}
Here's the result when compiling.
SDL window

Answer 1

You're only using a VGA size screen by defining these;
#define SCREEN_WIDTH 640
#define SCREEN_HEIGHT 480
Try this
int SCREEN_WIDTH=640;
int SCREEN_HEIGHT=480;
and add to main like this;
SDL_Window *window = SDL_CreateWindow( "Hello World", SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED, SCREEN_WIDTH, SCREEN_HEIGHT, SDL_WINDOW_ALLOW_HIGHDPI | SDL_WINDOW_OPENGL );
SDL_Renderer *renderer = SDL_CreateRenderer( window, -1, SDL_RENDERER_ACCELERATED | SDL_RENDERER_PRESENTVSYNC );
SDL_GL_GetDrawableSize(window,&SCREEN_WIDTH,&SCREEN_HEIGHT);