vkcube: Fix Cube Squishing on Resize

Modified viewport creation in vkcube to keep the
aspect ratio square and centered.

This change prevents cube from squishing and warping
when the window is resized.

It now shrinks and grows.

Change-Id: Ie2b3c5747293dfed968af5d83b581ac74d81bb10

1 files changed, 17 insertions, 3 deletions

diff --git a/cube/cube.cpp b/cube/cube.cpp
index abe80a88..4af97856 100644
--- a/cube/cube.cpp
+++ b/cube/cube.cpp
@@ -850,9 +850,23 @@ void Demo::draw_build_cmd(vk::CommandBuffer commandBuffer) {
     commandBuffer.bindPipeline(vk::PipelineBindPoint::eGraphics, pipeline);
     commandBuffer.bindDescriptorSets(vk::PipelineBindPoint::eGraphics, pipeline_layout, 0, 1,
                                      &swapchain_image_resources[current_buffer].descriptor_set, 0, nullptr);
-
-    auto const viewport =
-        vk::Viewport().setWidth((float)width).setHeight((float)height).setMinDepth((float)0.0f).setMaxDepth((float)1.0f);
+    float viewport_dimension;
+    float viewport_x = 0.0f;
+    float viewport_y = 0.0f;
+    if (width < height) {
+        viewport_dimension = (float)width;
+        viewport_y = (height - width) / 2.0f;
+    } else {
+        viewport_dimension = (float)height;
+        viewport_x = (width - height) / 2.0f;
+    }
+    auto const viewport = vk::Viewport()
+                              .setX(viewport_x)
+                              .setY(viewport_y)
+                              .setWidth((float)viewport_dimension)
+                              .setHeight((float)viewport_dimension)
+                              .setMinDepth((float)0.0f)
+                              .setMaxDepth((float)1.0f);
     commandBuffer.setViewport(0, 1, &viewport);
 
     vk::Rect2D const scissor(vk::Offset2D(0, 0), vk::Extent2D(width, height));