Examples: OpenGL2/3: Save/setup/restore viewport as part of render function. Update SDL example to match GL2 one. (fix #392)

examples/opengl3_example/imgui_impl_glfw_gl3.cpp

@@ -43,6 +43,7 @@ void ImGui_ImplGlfwGL3_RenderDrawLists(ImDrawData* draw_data)
 	GLint last_blend_dst; glGetIntegerv(GL_BLEND_DST, &last_blend_dst);
 	GLint last_blend_equation_rgb; glGetIntegerv(GL_BLEND_EQUATION_RGB, &last_blend_equation_rgb);
 	GLint last_blend_equation_alpha; glGetIntegerv(GL_BLEND_EQUATION_ALPHA, &last_blend_equation_alpha);
+    GLint last_viewport[4]; glGetIntegerv(GL_VIEWPORT, last_viewport);
 	GLboolean last_enable_blend = glIsEnabled(GL_BLEND);
 	GLboolean last_enable_cull_face = glIsEnabled(GL_CULL_FACE);
 	GLboolean last_enable_depth_test = glIsEnabled(GL_DEPTH_TEST);
@@ -62,7 +63,8 @@ void ImGui_ImplGlfwGL3_RenderDrawLists(ImDrawData* draw_data)
     float fb_height = io.DisplaySize.y * io.DisplayFramebufferScale.y;
     draw_data->ScaleClipRects(io.DisplayFramebufferScale);
 
-    // Setup orthographic projection matrix
+    // Setup viewport, orthographic projection matrix
+    glViewport(0, 0, (GLsizei)io.DisplaySize.x, (GLsizei)io.DisplaySize.y);
     const float ortho_projection[4][4] =
     {
         { 2.0f/io.DisplaySize.x, 0.0f,                   0.0f, 0.0f },
@@ -114,6 +116,7 @@ void ImGui_ImplGlfwGL3_RenderDrawLists(ImDrawData* draw_data)
 	if (last_enable_cull_face) glEnable(GL_CULL_FACE); else glDisable(GL_CULL_FACE);
 	if (last_enable_depth_test) glEnable(GL_DEPTH_TEST); else glDisable(GL_DEPTH_TEST);
 	if (last_enable_scissor_test) glEnable(GL_SCISSOR_TEST); else glDisable(GL_SCISSOR_TEST);
+    glViewport(last_viewport[0], last_viewport[1], (GLsizei)last_viewport[2], (GLsizei)last_viewport[3]);
 }
 
 static const char* ImGui_ImplGlfwGL3_GetClipboardText()

examples/opengl_example/imgui_impl_glfw.cpp

@@ -30,8 +30,8 @@ void ImGui_ImplGlfw_RenderDrawLists(ImDrawData* draw_data)
 {
     // We are using the OpenGL fixed pipeline to make the example code simpler to read!
     // Setup render state: alpha-blending enabled, no face culling, no depth testing, scissor enabled, vertex/texcoord/color pointers.
-    GLint last_texture;
-    glGetIntegerv(GL_TEXTURE_BINDING_2D, &last_texture);
+    GLint last_texture; glGetIntegerv(GL_TEXTURE_BINDING_2D, &last_texture);
+    GLint last_viewport[4]; glGetIntegerv(GL_VIEWPORT, last_viewport);
     glPushAttrib(GL_ENABLE_BIT | GL_COLOR_BUFFER_BIT | GL_TRANSFORM_BIT);
     glEnable(GL_BLEND);
     glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
@@ -49,7 +49,8 @@ void ImGui_ImplGlfw_RenderDrawLists(ImDrawData* draw_data)
     float fb_height = io.DisplaySize.y * io.DisplayFramebufferScale.y;
     draw_data->ScaleClipRects(io.DisplayFramebufferScale);
 
-    // Setup orthographic projection matrix
+    // Setup viewport, orthographic projection matrix
+    glViewport(0, 0, (GLsizei)io.DisplaySize.x, (GLsizei)io.DisplaySize.y);
     glMatrixMode(GL_PROJECTION);
     glPushMatrix();
     glLoadIdentity();
@@ -97,6 +98,7 @@ void ImGui_ImplGlfw_RenderDrawLists(ImDrawData* draw_data)
     glMatrixMode(GL_PROJECTION);
     glPopMatrix();
     glPopAttrib();
+    glViewport(last_viewport[0], last_viewport[1], (GLsizei)last_viewport[2], (GLsizei)last_viewport[3]);
 }
 
 static const char* ImGui_ImplGlfw_GetClipboardText()

examples/sdl_opengl_example/imgui_impl_sdl.cpp

@@ -22,8 +22,9 @@ static GLuint       g_FontTexture = 0;
 void ImGui_ImplSdl_RenderDrawLists(ImDrawData* draw_data)
 {
     // We are using the OpenGL fixed pipeline to make the example code simpler to read!
-    // A probable faster way to render would be to collate all vertices from all cmd_lists into a single vertex buffer.
     // Setup render state: alpha-blending enabled, no face culling, no depth testing, scissor enabled, vertex/texcoord/color pointers.
+    GLint last_texture; glGetIntegerv(GL_TEXTURE_BINDING_2D, &last_texture);
+    GLint last_viewport[4]; glGetIntegerv(GL_VIEWPORT, last_viewport);
     glPushAttrib(GL_ENABLE_BIT | GL_COLOR_BUFFER_BIT | GL_TRANSFORM_BIT);
     glEnable(GL_BLEND);
     glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
@@ -36,13 +37,17 @@ void ImGui_ImplSdl_RenderDrawLists(ImDrawData* draw_data)
     glEnable(GL_TEXTURE_2D);
     //glUseProgram(0); // You may want this if using this code in an OpenGL 3+ context
 
-    // Setup orthographic projection matrix
-    const float width = ImGui::GetIO().DisplaySize.x;
-    const float height = ImGui::GetIO().DisplaySize.y;
+    // 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;
+    draw_data->ScaleClipRects(io.DisplayFramebufferScale);
+
+    // Setup viewport, orthographic projection matrix
+    glViewport(0, 0, (GLsizei)io.DisplaySize.x, (GLsizei)io.DisplaySize.y);
     glMatrixMode(GL_PROJECTION);
     glPushMatrix();
     glLoadIdentity();
-    glOrtho(0.0f, width, height, 0.0f, -1.0f, +1.0f);
+    glOrtho(0.0f, io.DisplaySize.x, io.DisplaySize.y, 0.0f, -1.0f, +1.0f);
     glMatrixMode(GL_MODELVIEW);
     glPushMatrix();
     glLoadIdentity();
@@ -68,7 +73,7 @@ void ImGui_ImplSdl_RenderDrawLists(ImDrawData* draw_data)
             else
             {
                 glBindTexture(GL_TEXTURE_2D, (GLuint)(intptr_t)pcmd->TextureId);
-                glScissor((int)pcmd->ClipRect.x, (int)(height - pcmd->ClipRect.w), (int)(pcmd->ClipRect.z - pcmd->ClipRect.x), (int)(pcmd->ClipRect.w - pcmd->ClipRect.y));
+                glScissor((int)pcmd->ClipRect.x, (int)(fb_height - pcmd->ClipRect.w), (int)(pcmd->ClipRect.z - pcmd->ClipRect.x), (int)(pcmd->ClipRect.w - pcmd->ClipRect.y));
                 glDrawElements(GL_TRIANGLES, (GLsizei)pcmd->ElemCount, GL_UNSIGNED_SHORT, idx_buffer);
             }
             idx_buffer += pcmd->ElemCount;
@@ -80,12 +85,13 @@ void ImGui_ImplSdl_RenderDrawLists(ImDrawData* draw_data)
     glDisableClientState(GL_COLOR_ARRAY);
     glDisableClientState(GL_TEXTURE_COORD_ARRAY);
     glDisableClientState(GL_VERTEX_ARRAY);
-    glBindTexture(GL_TEXTURE_2D, 0);
+    glBindTexture(GL_TEXTURE_2D, last_texture);
     glMatrixMode(GL_MODELVIEW);
     glPopMatrix();
     glMatrixMode(GL_PROJECTION);
     glPopMatrix();
     glPopAttrib();
+    glViewport(last_viewport[0], last_viewport[1], (GLsizei)last_viewport[2], (GLsizei)last_viewport[3]);
 }
 
 static const char* ImGui_ImplSdl_GetClipboardText()