Artifact of the black line in the client area - opengl

Question

I have a black line artifact in the client area that disappears when the window is resized:
I called glViewport:
#define SDL_MAIN_HANDLED
#include <SDL2/SDL.h>
#include <glad/glad.h>
#include <iostream>
SDL_Window *window;
const float maxFPS = 5.f;
void fatalError(const std::string &message)
{
std::cout << message << std::endl;
if (window)
{
SDL_DestroyWindow(window);
}
SDL_Quit();
exit(-1);
}
int main()
{
if (SDL_Init(SDL_INIT_VIDEO) < 0)
{
fatalError("Failed to initialize");
}
SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1);
const int winW = 300;
const int winH = 300;
window = SDL_CreateWindow("OpenGL, SDL2, C++",
SDL_WINDOWPOS_CENTERED,
SDL_WINDOWPOS_CENTERED,
winW,
winH,
SDL_WINDOW_OPENGL);
if (!window)
{
fatalError("Failed to create the SDL window");
}
SDL_SetWindowResizable(window, SDL_TRUE);
SDL_GLContext glContext = SDL_GL_CreateContext(window);
if (!glContext)
{
fatalError("Failed to create the SDL_GL context");
}
if (!gladLoadGL())
{
fatalError("Failed to initialize the GLAD library");
}
glViewport(0, 0, winW, winH);
glClearColor(0.5f, 0.5f, 1.f, 1.f);
SDL_Event event;
bool running = true;
while (running)
{
while (SDL_PollEvent(&event))
{
switch (event.type)
{
case SDL_QUIT:
running = false;
break;
case SDL_WINDOWEVENT:
switch (event.window.event)
{
case SDL_WINDOWEVENT_RESIZED:
glViewport(0, 0, event.window.data1, event.window.data2);
break;
}
break;
}
}
float startTicks = SDL_GetTicks();
glClear(GL_COLOR_BUFFER_BIT);
SDL_GL_SwapWindow(window);
// Limit FPS to the max FPS
float frameTicks = SDL_GetTicks() - startTicks;
if (1000.f / maxFPS > frameTicks)
{
SDL_Delay(1000.f / maxFPS - frameTicks);
}
}
SDL_GL_DeleteContext(glContext);
SDL_DestroyWindow(window);
SDL_Quit();
return 0;
}
makefile
# build command: mingw32-make
# -mwindows - a key to hide the console
INC = -I"E:\Libs\SDL2-2.24.0-mingw-64bit\include" \
-I"E:\Libs\glad-0.1.36-mingw-64bit\include"
LIB = -L"E:\Libs\SDL2-2.24.0-mingw-64bit\lib" \
-L"E:\Libs\glad-0.1.36-mingw-64bit\lib"
all: main.o
g++ main.o $(LIB) -lSDL2.dll -lglad -o app.exe
main.o: main.cpp
g++ -c $(INC) main.cpp
The same topic on the official SDL2 forum: https://discourse.libsdl.org/t/artifact-of-the-black-line-in-the-client-area/39110
Not sure if it matters but the
docs says you should
call SDL_GL_SetAttribute before creating the window.
#Peter87 I tried it but everything the same:
int main()
{
if (SDL_Init(SDL_INIT_VIDEO) < 0)
{
fatalError("Failed to initialize");
}
SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1);
const int winW = 300;
const int winH = 300;
window = SDL_CreateWindow("OpenGL, SDL2, C++",
SDL_WINDOWPOS_CENTERED,
SDL_WINDOWPOS_CENTERED,
winW,
winH,
SDL_WINDOW_OPENGL);
if (!window)
{
fatalError("Failed to create the SDL window");
}
SDL_SetWindowResizable(window, SDL_TRUE);
SDL_GLContext glContext = SDL_GL_CreateContext(window);
if (!glContext)
{
fatalError("Failed to create the SDL_GL context");
}

Answer 1

It appears to be a SDL bug, though for me the effect was different (the window wasn't resizable at all).
Instead of calling SDL_SetWindowResizable(window, SDL_TRUE);, pass SDL_WINDOW_RESIZABLE when creating the window.