I am on an Ubuntu 19.10 64 bit system
Source files:
https://drive.google.com/open?id=1I4ejOHNXqbAOkTbIyJR0lvldsAwiPPqI
Problem:
I am working on a simple drawing program using gtk and glade with c. Right now I am stuck into implementing undoing behavior. I have two problems. There are cases for when I press the undo button.
1)
When I have one stroke or one dot on the canvas, it works perfect as I experienced. Canvas clears itself.
2)
When I have two strokes or two dots on the canvas, if I click undo once, canvas does not redraw itself, unless I draw again; if I click twice, it works perfect like in the first case, canvas clears.
3)
When I have more than two strokes or two dots on the canvas, if I click undo twice, the program stops working waiting me to force quit.
I am a beginner at using glade, gtk3, and cairo libraries. I have been searching about the issue for days. However, the resources are scarce compared to trending frameworks and libraries. Furthermore, I couldn't match the problem I need. I appreciate any help.
EDIT I forgot to add that the halting problem occurs after the function , on_undo_clicked exits the second time (twice undo click).
I solved the problem.
In the function, addPoint I forgot that the next struct pointer's pre pointer may be a dangling pointer. It creates the problem.
Related
I am new to Xlib (in C) and am having two issues when calling the XMoveResizeWindow function.
ex.
XMoveResizeWindow(display, window_id, move_x, move_y, resize_x, resize_y);
1) After the call, the window I move will reposition itself correctly, however, if I select the window with the pointer after the move, it will instantly revert back to the position it held prior to the move. I assume I have to somehow 'update' the X11 server after it's moved with the windows new position?
2) Secondly, in regards to the resize of the window. My window is essentially being truncated by the x and y values entered, instead of resized. In other words, instead of the entire window shrinking down, the right and bottom sides of the window are cut off from view. Is there a way to instead resize the entire window?
--I am sorry I am unable to submit my complete code, however, I believe my issues are due solely to my lack of understanding of Xlib and this particular function's operations. As such, I am not neccessarily looking for specific code as a solution, merely an explination or suggestion on how I should go about implementing a solution.
Thank you.
I believe there is something wrong with your code, since that code is not available i'll point to an example.
Examples are given at readme itself.
During the development of my program I came across one drawing glitch that I was unable to solve. I am using GtkRevealer to show and hide a GtkInfoBar above another box holding a scrolled window with a GtkTextView (actually GtkSourceView) a lot like it is in gedit.
The whole thing is packed in a GtkPaned.
When I hide the infobar through the revealer, a black area in the text view appears and it disappears when a redrawing of the widget must occur (for instance when I click on the text view to place the cursor)
Additionally, this glitch does not appear if I enlarge the default resolution of the window, which for compatibility reasons is 640x480.
I understand that this may be hard to reproduce, but I am unaware who encountered the same problem. He maybe knows a workaround to this issue.
Also any idea is welcome.
I will draw exactly how the glitch looks on gedit (although it doesn't happen in gedit or it does but I cannot hit the correct resolution).
I tried to force a redrawing with gtk_widget_queue_draw() but nothing happens and it won't, because it has nothing to redraw.
I will try now to place the cursor automatically. It may work, but it is not functionally adequate.
EDIT:
Surprisingly it did not work. Grabbing the focus and placing the cursor
had no effect on the glitched visual behavior. I had to even make a new line
to fix it this time.
The fact that I have to resize the window with a value more than a specific point, may mean that the glitch may be due to alignment miscaulculations, but this doesn't explain why adding new line or a text mark in the gutter that colorizes the entire line also removes the black field.
Currently this bug has been encountered in another programs with a text view as well, but hasn't been reported as a bug yet.
Perhaps this has something to do with the fact that it is hard to reproduce.
I found that hiding the gtk text view with gtk_widget_hide() and then showing it with gtk_widget_show() works. The flicker of this visual glitch is not noticeable, perhaps due to GTK+ being event-based and waiting for the function to return to process changes.
I'm currently getting back to some Windows Programming using Petzold's book (5th edition).
I compiled the following example using BitBlt and it doesn't work as it is supposed to.
It should copy the Window's icon of (CxSource, CySource) size and replicate it on the whole window's surface.
What happens, in reality, using Windows 7 is that the bitmap below the window gets sourced and copied into the drawing surface i.e. hdcClient.
I don't understand why it behaves like this knowing that it's clear the DC passed to BitBlt is hdcWindow, which refers to a device context obtained via a GetWindowDC(hwnd) of the current application.
I first thought it was due to the fact the transparency mode is enabled by default, but deactivating it doesn't change anything. BitBlt seems to always take the surface below the application Window!
I don't get it! :)
Anyone knows why it works that way and how to fix it?
Making screenshots with BitBlt() did not exactly get any easier since the addition of the DWM (Desktop Window Manager, aka Aero). Petzold's sample code suffers from a subtle timing issue, it is making the screenshot too soon. It does so while Aero is still busy animating the frame, fading it into view. So you see what is behind the window, possibly already partly faded depending on how quickly the first WM_PAINT message is generated.
You can easily fix it by disabling the effect:
#include <windows.h>
#include <dwmapi.h>
#pragma comment(lib, "dwmapi.lib")
And after the CreateWindow() call:
BOOL disabled = TRUE;
DwmSetWindowAttribute(hwnd, DWMWA_TRANSITIONS_FORCEDISABLED, &disabled, sizeof(disabled));
Another tricky detail is that the first BitBlt matters, the DWM returns a cached copy afterwards that is not correctly invalidated by the animation.
This gets grittier when you need a screenshot of a window that belongs to another process. But that was already an issue before Aero, you had to wait long enough to ensure that the window was fully painted. Notable perhaps is the perf of BitBlt(), it gets bogged-down noticeably by having to do job of composing the final image from the window back-buffers. Lots of questions about that at SO, without happy answers.
It is not supposed to copy the windows icon, it is supposed to copy the windows titlebar part where the icon is located.
There are some issues with this (now 20 year old code):
GetSystemMetrics values cannot be used for window related dimensions anymore since GetSystemMetrics returns the classic sizes, not the Visual Style sizes.
Depending on the Windows version, the DWM might define the window size as something larger than your window (where it draws the window shadow and other effects).
Your example works OK on XP:
(There is a small problem because the titlebar is not square (unlike Windows 98/2000 that this example was designed for) so you see a issue in the top left where it is just white. I also modified the example slightly so it varies the HDC source location)
On a modern version of Windows it seems like the DWM or something is not able to properly emulate a simple window DC and parts of the shadow/border/effects area is part of the DC:
I don't know how to fix this but the example is pretty useless anyway, if you want to draw the window icon you should draw the HICON with DrawIconEx. If you want to draw custom non-client area stuff then you need to find more recent examples, not something that only supports the classic theme.
How would one "lock" the mouse to a certain OpenGL window. Sort of like how it is done in Minecraft.
Is GameDev a better place to ask?
Like Robert said in the comment, OpenGL doesn't actually do user input.
However, there are libraries that can abstract the platform dependent part away, such as LibSDL. You can use it to grab the mouse to your window.
A similar question has been asked here, where a programmer used a class called robot to change the mouse position.
Code: Robot.moveMouse(x,y)
This code was written in java, however, There are several classes like robot that can do the trick!
One option is to constantly move the mouse to the center of the screen or wherever you want it.
I want to find C / Xorg code to 'enter' a left mouse button click. I'd expect a single line of code but the only things I've found written in C are about two dozen lines long and they don't work anyway :( It seems it can be done in Windows, but I'm in Linux.
The reason for the question is that I've written a utility that lets me move my mouse pointer between several screens using the keyboard. The only problem is that if I move to a location where window abc used to be but another window xyz has been loaded on top of that same location, the mouse pointer moves to xyz just fine, but xyz doesn't have focus -- until I left click the mouse. So, I want to build the 'click' into my code.
The code I tried that didn't work was based on XSendEvent().
Yes, I've more or less come to understand. Anyway it seems this is the way:
{
#include <X11/extensions/XTest.h>
XTestFakeButtonEvent(display, 1, True, CurrentTime);
XTestFakeButtonEvent(display, 1, False, CurrentTime);
XFlush(display);
}
... and add " -lXtst " to the LDFLAGS line in the Makefile.
Xlib seems to be so bloody difficult. I've had advice to use other libraries, I wish I knew how to go about changing over.
Thanks R.
Why not just directly raise/focus the window rather than trying to make a fake click event? That should be a lot more reliable and work with all window managers, even non-click-to-focus ones.
xdotool is the easy way of doing this. It's a command line tool. You can use it in simple scripts. For example:
#!/bin/sh
xdotool mousemove x y
xdotool click 1