OpenGL rendering on entire screen

[androbytes]

I have some code that is supposed to only make the window screen change colour, but the entire thing is, it also hides the top bar.

static void draw_callback(const ImDrawList* parent_list, const ImDrawCmd* cmd)
{
	glViewport(0, 0, 300, 300);
	glClearColor(1.0f, 1.0f, 1.0f, 1.0f);
	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
	glViewport(Core::GetScreenSize(window).x/2, Core::GetScreenSize(window).y/2, Core::GetScreenSize(window).x, Core::GetScreenSize(window).y);
}

int main() {
   while (!glfwWindowShouldClose(window)) {
        ImGui_ImplOpenGL3_NewFrame();
	ImGui_ImplGlfw_NewFrame();
	ImGui::NewFrame();

	// Dockspace
	ImGui::DockSpaceOverViewport(ImGui::GetMainViewport());
        ImGui::Begin("Viewport");

        ImGui::GetWindowDrawList()->AddCallback(draw_callback, NULL);

        ImGui::End();

        ImGui::Render();
	int w, h;
	glfwGetFramebufferSize(window, &w, &h);
	glViewport(0, 0, w, h);
	glClearColor(0.45f, 0.55f, 0.60f, 1.00f);
	glClear(GL_COLOR_BUFFER_BIT);
	ImGui_ImplOpenGL3_RenderDrawData(ImGui::GetDrawData());

	if (io.ConfigFlags & ImGuiConfigFlags_ViewportsEnable)
	{
		GLFWwindow* backup_current_context = glfwGetCurrentContext();
		ImGui::UpdatePlatformWindows();
		ImGui::RenderPlatformWindowsDefault();
		glfwMakeContextCurrent(backup_current_context);
	}

	/*End of rendering*/

	glfwPollEvents();
	glfwSwapBuffers(window);
    }

[PathogenDavid]

glClear is not affected by the current viewport.

If I remember right you can use glScissor instead (make sure you enable it with glEnable(GL_SCISSOR_TEST).)

Edit: Also, why not just use ImGuiDrawList::AddRectFilled?

[androbytes]

https://gist.github.com/AnnoyingB/545a70a872fe4dfaddf8a3be7da93a0d

I am using GLEW and GLFW.

[PathogenDavid]

Thanks! Although I was hoping you'd share your attempt at getting it to render to an FBO. Or are you not sure where to start in general?

[PathogenDavid]

Actually I think I can infer based on your earlier comment #4590 (reply in thread) (I must admit I didn't look at it very closely the other day.)

I don't think you can use glGenBuffers/glBindBuffer with FBOs like that. You need to use glGenFrameBuffers/glBindFramebuffer instead. It's been too long since I've learned OpenGL to recommend a specific tutorial, but at a glance this one looks pretty reasonable: https://learnopengl.com/Advanced-OpenGL/Framebuffers

(You might consider enabling OpenGL's debug context to catch these sorts of mistakes. See the second half of this guide or the OpenGL wiki)

[androbytes]

Ah, I have understood framebuffers. This is what I used: http://www.opengl-tutorial.org/intermediate-tutorials/tutorial-14-render-to-texture/. Thanks for using your time to help me!

[PathogenDavid]

No problem, glad I could help!