Fixed scissoring in OpenGL example

examples/opengl_example/main.cpp

@@ -24,7 +24,7 @@ static void ImImpl_RenderDrawLists(ImDrawList** const cmd_lists, int cmd_lists_c
 	glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
 	glDisable(GL_CULL_FACE);
 	glDisable(GL_DEPTH_TEST);
-	//glEnable(GL_SCISSOR_TEST);
+	glEnable(GL_SCISSOR_TEST);
 	glEnableClientState(GL_VERTEX_ARRAY);
 	glEnableClientState(GL_TEXTURE_COORD_ARRAY);
 	glEnableClientState(GL_COLOR_ARRAY);
@@ -34,9 +34,11 @@ static void ImImpl_RenderDrawLists(ImDrawList** const cmd_lists, int cmd_lists_c
 	glEnable(GL_TEXTURE_2D);
 
 	// Setup matrices
+	const float width = ImGui::GetIO().DisplaySize.x;
+	const float height = ImGui::GetIO().DisplaySize.y;
 	glMatrixMode(GL_PROJECTION);
 	glLoadIdentity();
-	glOrtho(0.0f, ImGui::GetIO().DisplaySize.x, ImGui::GetIO().DisplaySize.y, 0.0f, -1.0f, +1.0f);
+	glOrtho(0.0f, width, height, 0.0f, -1.0f, +1.0f);
 	glMatrixMode(GL_MODELVIEW);
 	glLoadIdentity();
 
@@ -53,7 +55,7 @@ static void ImImpl_RenderDrawLists(ImDrawList** const cmd_lists, int cmd_lists_c
 		const ImDrawCmd* pcmd_end = cmd_list->commands.end();
 		for (const ImDrawCmd* pcmd = cmd_list->commands.begin(); pcmd != pcmd_end; pcmd++)
 		{
-			glScissor((int)pcmd->clip_rect.x, (int)pcmd->clip_rect.y, (int)(pcmd->clip_rect.z - pcmd->clip_rect.x), (int)(pcmd->clip_rect.w - pcmd->clip_rect.y));
+			glScissor((int)pcmd->clip_rect.x, (int)(height - pcmd->clip_rect.w), (int)(pcmd->clip_rect.z - pcmd->clip_rect.x), (int)(pcmd->clip_rect.w - pcmd->clip_rect.y));
 			glDrawArrays(GL_TRIANGLES, vtx_offset, pcmd->vtx_count);
 			vtx_offset += pcmd->vtx_count;
 		}