Examples: OpenGL: Tentative fix for miscaled call to glViewport on high-DPI screens (#441)

Fix for 980ca286fe

examples/opengl3_example/imgui_impl_glfw_gl3.cpp

@@ -60,11 +60,12 @@ void ImGui_ImplGlfwGL3_RenderDrawLists(ImDrawData* draw_data)
 
     // Handle cases of screen coordinates != from framebuffer coordinates (e.g. retina displays)
     ImGuiIO& io = ImGui::GetIO();
-    float fb_height = io.DisplaySize.y * io.DisplayFramebufferScale.y;
+    int fb_width = (int)(io.DisplaySize.x * io.DisplayFramebufferScale.x);
+    int fb_height = (int)(io.DisplaySize.y * io.DisplayFramebufferScale.y);
     draw_data->ScaleClipRects(io.DisplayFramebufferScale);
 
     // Setup viewport, orthographic projection matrix
-    glViewport(0, 0, (GLsizei)io.DisplaySize.x, (GLsizei)io.DisplaySize.y);
+    glViewport(0, 0, (GLsizei)fb_width, (GLsizei)fb_height);
     const float ortho_projection[4][4] =
     {
         { 2.0f/io.DisplaySize.x, 0.0f,                   0.0f, 0.0f },

examples/opengl_example/imgui_impl_glfw.cpp

@@ -46,11 +46,12 @@ void ImGui_ImplGlfw_RenderDrawLists(ImDrawData* draw_data)
 
     // Handle cases of screen coordinates != from framebuffer coordinates (e.g. retina displays)
     ImGuiIO& io = ImGui::GetIO();
-    float fb_height = io.DisplaySize.y * io.DisplayFramebufferScale.y;
+    int fb_width = (int)(io.DisplaySize.x * io.DisplayFramebufferScale.x);
+    int fb_height = (int)(io.DisplaySize.y * io.DisplayFramebufferScale.y);
     draw_data->ScaleClipRects(io.DisplayFramebufferScale);
 
     // Setup viewport, orthographic projection matrix
-    glViewport(0, 0, (GLsizei)io.DisplaySize.x, (GLsizei)io.DisplaySize.y);
+    glViewport(0, 0, (GLsizei)fb_width, (GLsizei)fb_height);
     glMatrixMode(GL_PROJECTION);
     glPushMatrix();
     glLoadIdentity();

examples/sdl_opengl3_example/imgui_impl_sdl_gl3.cpp

@@ -55,11 +55,12 @@ void ImGui_ImplSdlGL3_RenderDrawLists(ImDrawData* draw_data)
 
 	// Handle cases of screen coordinates != from framebuffer coordinates (e.g. retina displays)
 	ImGuiIO& io = ImGui::GetIO();
-	float fb_height = io.DisplaySize.y * io.DisplayFramebufferScale.y;
+    int fb_width = (int)(io.DisplaySize.x * io.DisplayFramebufferScale.x);
+    int fb_height = (int)(io.DisplaySize.y * io.DisplayFramebufferScale.y);
 	draw_data->ScaleClipRects(io.DisplayFramebufferScale);
 
 	// Setup orthographic projection matrix
-    glViewport(0, 0, (GLsizei)io.DisplaySize.x, (GLsizei)io.DisplaySize.y);
+    glViewport(0, 0, (GLsizei)fb_width, (GLsizei)fb_height);
 	const float ortho_projection[4][4] =
 	{
 		{ 2.0f/io.DisplaySize.x, 0.0f,                   0.0f, 0.0f },

examples/sdl_opengl_example/imgui_impl_sdl.cpp

@@ -39,11 +39,12 @@ void ImGui_ImplSdl_RenderDrawLists(ImDrawData* draw_data)
 
     // Handle cases of screen coordinates != from framebuffer coordinates (e.g. retina displays)
     ImGuiIO& io = ImGui::GetIO();
-    float fb_height = io.DisplaySize.y * io.DisplayFramebufferScale.y;
+    int fb_width = (int)(io.DisplaySize.x * io.DisplayFramebufferScale.x);
+    int fb_height = (int)(io.DisplaySize.y * io.DisplayFramebufferScale.y);
     draw_data->ScaleClipRects(io.DisplayFramebufferScale);
 
     // Setup viewport, orthographic projection matrix
-    glViewport(0, 0, (GLsizei)io.DisplaySize.x, (GLsizei)io.DisplaySize.y);
+    glViewport(0, 0, (GLsizei)fb_width, (GLsizei)fb_height);
     glMatrixMode(GL_PROJECTION);
     glPushMatrix();
     glLoadIdentity();