Improve model-viewer support for lights (#626)

* Improve model-viewer support for lights

The main visible change here is that the model-viewer example supports
multiple light sources, with a basic UI for adding new light sources to
the scene, and for manipulating the ones that are there.

Along the way I also refactored the `IMaterial` decomposition to be a
bit less naive, while still only including a completely naive
Blinn-Phong implementation.

I also went ahead and spruced up the `cube.obj` file so that it has
multiple materials, although it is still a completely uninteresting
asset.

* Fixup: Windows SDK version

1 files changed, 19 insertions, 2 deletions

diff --git a/tools/gfx/gui.cpp b/tools/gfx/gui.cpp
index 85a080526..cefb132fb 100644
--- a/tools/gfx/gui.cpp
+++ b/tools/gfx/gui.cpp
@@ -13,7 +13,24 @@ namespace gfx {
 #ifdef _WIN32
 LRESULT CALLBACK guiWindowProc(HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam)
 {
-    return ImGui_ImplWin32_WndProcHandler(hWnd, msg, wParam, lParam);
+    LRESULT handled = ImGui_ImplWin32_WndProcHandler(hWnd, msg, wParam, lParam);
+    if(handled) return handled;
+    ImGuiIO& io = ImGui::GetIO();
+
+    switch( msg )
+    {
+    case WM_LBUTTONDOWN:
+    case WM_LBUTTONUP:
+        if(io.WantCaptureMouse) handled = 1;
+        break;
+
+    case WM_KEYDOWN:
+    case WM_KEYUP:
+        if(io.WantCaptureKeyboard) handled = 1;
+        break;
+    }
+
+    return handled;
 }
 void setNativeWindowHook(Window* window, WNDPROC proc);
 #endif
@@ -314,7 +331,7 @@ void GUI::endFrame()
     viewport.extentX = draw_data->DisplaySize.x;
     viewport.extentY = draw_data->DisplaySize.y;
     viewport.minZ = 0;
-    viewport.maxZ = 0;
+    viewport.maxZ = 1;
 
     renderer->setViewport(viewport);