Preserve 16:9 tile aspect on resize

TileLayout.cpp

@@ -21,46 +21,116 @@ std::vector<Vertex> makeQuad(
         {{x0, y1}, {0.0f, 1.0f}},
     };
 }
+
+float toNdcX(float x, float viewportWidth)
+{
+    return x * 2.0f / viewportWidth - 1.0f;
 }
 
-std::vector<Vertex> makeGridLayout(
+float toNdcY(float y, float viewportHeight)
+{
+    return y * 2.0f / viewportHeight - 1.0f;
+}
+}
+
+std::vector<TileRect> makeGridTileRects(
     uint32_t cols,
     uint32_t rows,
-    float gapX,
+    float viewportWidth,
-    float gapY)
+    float viewportHeight,
+    float gapPixels,
+    float targetAspect)
 {
-    std::vector<Vertex> vertices;
+    std::vector<TileRect> rects;
-    vertices.reserve(
+    rects.reserve(static_cast<size_t>(cols) * rows);
-        static_cast<size_t>(cols) * rows * 6);
 
-    const float tileW =
+    if (cols == 0 || rows == 0 ||
-        (2.0f - gapX * static_cast<float>(cols - 1)) /
+        viewportWidth <= 0.0f || viewportHeight <= 0.0f ||
+        targetAspect <= 0.0f)
+    {
+        return rects;
+    }
+
+    const float gapX =
+        std::min(gapPixels, viewportWidth * 0.1f);
+    const float gapY =
+        std::min(gapPixels, viewportHeight * 0.1f);
+
+    const float cellW =
+        (viewportWidth - gapX * static_cast<float>(cols - 1)) /
         static_cast<float>(cols);
-    const float tileH =
+    const float cellH =
-        (2.0f - gapY * static_cast<float>(rows - 1)) /
+        (viewportHeight - gapY * static_cast<float>(rows - 1)) /
         static_cast<float>(rows);
 
+    float tileW = cellW;
+    float tileH = tileW / targetAspect;
+
+    if (tileH > cellH)
+    {
+        tileH = cellH;
+        tileW = tileH * targetAspect;
+    }
+
+    const float insetX = (cellW - tileW) * 0.5f;
+    const float insetY = (cellH - tileH) * 0.5f;
+
     for (uint32_t row = 0; row < rows; ++row)
     {
         for (uint32_t col = 0; col < cols; ++col)
         {
             const float x0 =
-                -1.0f +
+                static_cast<float>(col) * (cellW + gapX) +
-                static_cast<float>(col) * (tileW + gapX);
+                insetX;
             const float y0 =
-                -1.0f +
+                static_cast<float>(row) * (cellH + gapY) +
-                static_cast<float>(row) * (tileH + gapY);
+                insetY;
             const float x1 = x0 + tileW;
             const float y1 = y0 + tileH;
 
-            auto quad = makeQuad(x0, y0, x1, y1);
+            rects.push_back({x0, y0, x1, y1});
-            vertices.insert(
-                vertices.end(),
-                quad.begin(),
-                quad.end());
         }
     }
 
+    return rects;
+}
+
+std::vector<Vertex> makeGridLayout(
+    uint32_t cols,
+    uint32_t rows,
+    float viewportWidth,
+    float viewportHeight,
+    float gapPixels,
+    float targetAspect)
+{
+    std::vector<Vertex> vertices;
+    vertices.reserve(
+        static_cast<size_t>(cols) * rows * 6);
+
+    std::vector<TileRect> rects =
+        makeGridTileRects(
+            cols,
+            rows,
+            viewportWidth,
+            viewportHeight,
+            gapPixels,
+            targetAspect
+        );
+
+    for (const TileRect& rect : rects)
+    {
+        auto quad = makeQuad(
+            toNdcX(rect.x0, viewportWidth),
+            toNdcY(rect.y0, viewportHeight),
+            toNdcX(rect.x1, viewportWidth),
+            toNdcY(rect.y1, viewportHeight)
+        );
+        vertices.insert(
+            vertices.end(),
+            quad.begin(),
+            quad.end());
+    }
+
     return vertices;
 }
 
@@ -68,11 +138,20 @@ void updateGridLayout(
     Vertex* vertices,
     uint32_t cols,
     uint32_t rows,
-    float gapX,
+    float viewportWidth,
-    float gapY)
+    float viewportHeight,
+    float gapPixels,
+    float targetAspect)
 {
     std::vector<Vertex> updated =
-        makeGridLayout(cols, rows, gapX, gapY);
+        makeGridLayout(
+            cols,
+            rows,
+            viewportWidth,
+            viewportHeight,
+            gapPixels,
+            targetAspect
+        );
 
     std::copy(
         updated.begin(),

TileLayout.hpp

@@ -9,18 +9,38 @@ struct Vertex
     float uv[2];
 };
 
+struct TileRect
+{
+    float x0;
+    float y0;
+    float x1;
+    float y1;
+};
+
+std::vector<TileRect> makeGridTileRects(
+    uint32_t cols,
+    uint32_t rows,
+    float viewportWidth,
+    float viewportHeight,
+    float gapPixels,
+    float targetAspect);
+
 std::vector<Vertex> makeGridLayout(
     uint32_t cols,
     uint32_t rows,
-    float gapX,
+    float viewportWidth,
-    float gapY);
+    float viewportHeight,
+    float gapPixels,
+    float targetAspect);
 
 void updateGridLayout(
     Vertex* vertices,
     uint32_t cols,
     uint32_t rows,
-    float gapX,
+    float viewportWidth,
-    float gapY);
+    float viewportHeight,
+    float gapPixels,
+    float targetAspect);
 
 void updateUvForAspectRatio(
     Vertex* vertices,

main.cpp

@@ -37,6 +37,7 @@ constexpr uint32_t TEXTURE_WIDTH = 512;
 constexpr uint32_t TEXTURE_HEIGHT = 288;
 constexpr uint32_t VERTICES_PER_QUAD = 6;
 constexpr float TILE_GAP_PIXELS = 8.0f;
+constexpr float TILE_ASPECT = 16.0f / 9.0f;
 
 static std::atomic<bool> g_running{true};
 
@@ -465,32 +466,23 @@ static void drawTileLabels(
     ImDrawList* drawList = ImGui::GetForegroundDrawList();
     const ImVec2 displaySize = ImGui::GetIO().DisplaySize;
 
-    const float gapX =
+    const std::vector<TileRect> tileRects =
-        std::min(TILE_GAP_PIXELS, displaySize.x * 0.1f);
+        makeGridTileRects(
-    const float gapY =
+            gridCols,
-        std::min(TILE_GAP_PIXELS, displaySize.y * 0.1f);
+            gridRows,
-    const float tileW =
+            displaySize.x,
-        (displaySize.x -
+            displaySize.y,
-            gapX * static_cast<float>(gridCols - 1)) /
+            TILE_GAP_PIXELS,
-        static_cast<float>(gridCols);
+            TILE_ASPECT
-    const float tileH =
+        );
-        (displaySize.y -
-            gapY * static_cast<float>(gridRows - 1)) /
-        static_cast<float>(gridRows);
     const float labelH =
         std::max(24.0f, ImGui::GetFontSize() + 10.0f);
 
-    for (uint32_t i = 0; i < feeds.size(); ++i)
+    for (uint32_t i = 0;
+         i < feeds.size() && i < tileRects.size();
+         ++i)
     {
-        const uint32_t col = i % gridCols;
+        const TileRect& tileRect = tileRects[i];
-        const uint32_t row = i / gridCols;
-
-        const float x0 =
-            static_cast<float>(col) * (tileW + gapX);
-        const float y0 =
-            static_cast<float>(row) * (tileH + gapY);
-        const float x1 = x0 + tileW;
-        const float y1 = y0 + tileH;
 
         const FeedRuntimeStatus status =
             feeds[i]->status();
@@ -503,9 +495,15 @@ static void drawTileLabels(
                 ? feedRuntimeStatusDisplayName(status)
                 : sourceInfo);
 
-        const ImVec2 labelMin(x0, y1 - labelH);
+        const ImVec2 labelMin(
-        const ImVec2 labelMax(x1, y1);
+            tileRect.x0,
-        const ImVec2 textPos(x0 + 10.0f, y1 - labelH + 5.0f);
+            tileRect.y1 - labelH
+        );
+        const ImVec2 labelMax(tileRect.x1, tileRect.y1);
+        const ImVec2 textPos(
+            tileRect.x0 + 10.0f,
+            tileRect.y1 - labelH + 5.0f
+        );
 
         drawList->AddRectFilled(
             labelMin,
@@ -630,19 +628,14 @@ int main(int argc, char* argv[])
     // Vertex buffer (quad tiles)
     // ----------------------------------------
 
-    const float initialGapX =
-        2.0f * TILE_GAP_PIXELS /
-        static_cast<float>(winWidth);
-    const float initialGapY =
-        2.0f * TILE_GAP_PIXELS /
-        static_cast<float>(winHeight);
-
     std::vector<Vertex> quadVertices =
         makeGridLayout(
             config.gridCols,
             config.gridRows,
-            initialGapX,
+            static_cast<float>(winWidth),
-            initialGapY);
+            static_cast<float>(winHeight),
+            TILE_GAP_PIXELS,
+            TILE_ASPECT);
 
     VkDeviceSize vbSize =
         sizeof(quadVertices[0]) * quadVertices.size();
@@ -1680,34 +1673,16 @@ int main(int argc, char* argv[])
             SDL_GetPerformanceCounter();
 
         VkExtent2D swapExtent = swapchain.extent();
-        const float gapX =
-            2.0f * TILE_GAP_PIXELS /
-            static_cast<float>(swapExtent.width);
-        const float gapY =
-            2.0f * TILE_GAP_PIXELS /
-            static_cast<float>(swapExtent.height);
-
         updateGridLayout(
             quadVertices.data(),
             config.gridCols,
             config.gridRows,
-            gapX,
+            static_cast<float>(swapExtent.width),
-            gapY
+            static_cast<float>(swapExtent.height),
+            TILE_GAP_PIXELS,
+            TILE_ASPECT
         );
 
-        const float tileWidthPx =
-            (static_cast<float>(swapExtent.width) -
-                TILE_GAP_PIXELS *
-                    static_cast<float>(config.gridCols - 1)) /
-            static_cast<float>(config.gridCols);
-        const float tileHeightPx =
-            (static_cast<float>(swapExtent.height) -
-                TILE_GAP_PIXELS *
-                    static_cast<float>(config.gridRows - 1)) /
-            static_cast<float>(config.gridRows);
-        const float tileAspect =
-            tileWidthPx / tileHeightPx;
-
         for (uint32_t i = 0; i < feedCount; ++i)
         {
             float srcAspect = feeds[i]->srcAspectRatio();
@@ -1716,7 +1691,7 @@ int main(int argc, char* argv[])
                 quadVertices.data(),
                 i,
                 srcAspect,
-                tileAspect);
+                TILE_ASPECT);
         }
 
         std::memcpy(