From 2cf4a42cbe0c65464ead0ef30b8375a48138f359 Mon Sep 17 00:00:00 2001
From: Matt <m.moninger.h@gmail.com>
Date: Sun, 23 Jun 2019 02:06:59 +0200
Subject: [PATCH] Add rain rendering to OpenGL renderer

---
 .../engines/opengl/OpenGLDrawingEngine.cpp    | 64 ++++++++++++++++++-
 src/openrct2/drawing/Rain.h                   | 10 +++
 src/openrct2/drawing/X8DrawingEngine.cpp      | 10 ---
 3 files changed, 71 insertions(+), 13 deletions(-)

diff --git a/src/openrct2-ui/drawing/engines/opengl/OpenGLDrawingEngine.cpp b/src/openrct2-ui/drawing/engines/opengl/OpenGLDrawingEngine.cpp
index 0316349754..6fa92e46e6 100644
--- a/src/openrct2-ui/drawing/engines/opengl/OpenGLDrawingEngine.cpp
+++ b/src/openrct2-ui/drawing/engines/opengl/OpenGLDrawingEngine.cpp
@@ -56,7 +56,6 @@ class OpenGLDrawingContext final : public IDrawingContext
 private:
     OpenGLDrawingEngine* _engine = nullptr;
     rct_drawpixelinfo* _dpi = nullptr;
-
     ApplyTransparencyShader* _applyTransparencyShader = nullptr;
     DrawLineShader* _drawLineShader = nullptr;
     DrawRectShader* _drawRectShader = nullptr;
@@ -115,6 +114,62 @@ public:
     void HandleTransparency();
 
     void SetDPI(rct_drawpixelinfo* dpi);
+    rct_drawpixelinfo* GetDPI() const
+    {
+        return _dpi;
+    }
+};
+
+class OpenGLRainDrawer final : public IRainDrawer
+{
+    OpenGLDrawingContext* _drawingContext;
+
+public:
+    explicit OpenGLRainDrawer(OpenGLDrawingContext* drawingContext)
+        : _drawingContext(drawingContext)
+    {
+    }
+
+    virtual void Draw(int32_t x, int32_t y, int32_t width, int32_t height, int32_t xStart, int32_t yStart)
+    {
+        const uint8_t* pattern = RainPattern;
+
+        uint8_t patternXSpace = *pattern++;
+        uint8_t patternYSpace = *pattern++;
+
+        uint8_t patternStartXOffset = xStart % patternXSpace;
+        uint8_t patternStartYOffset = yStart % patternYSpace;
+
+        const auto* dpi = _drawingContext->GetDPI();
+
+        uint32_t pixelOffset = (dpi->pitch + dpi->width) * y + x;
+        uint8_t patternYPos = patternStartYOffset % patternYSpace;
+
+        for (; height != 0; height--)
+        {
+            uint8_t patternX = pattern[patternYPos * 2];
+            if (patternX != 0xFF)
+            {
+                uint32_t finalPixelOffset = width + pixelOffset;
+
+                uint32_t xPixelOffset = pixelOffset;
+                xPixelOffset += ((uint8_t)(patternX - patternStartXOffset)) % patternXSpace;
+
+                uint8_t patternPixel = pattern[patternYPos * 2 + 1];
+                for (; xPixelOffset < finalPixelOffset; xPixelOffset += patternXSpace)
+                {
+                    int32_t pixelX = xPixelOffset % dpi->width;
+                    int32_t pixelY = (xPixelOffset / dpi->width) % dpi->height;
+
+                    _drawingContext->DrawLine(patternPixel, pixelX, pixelY, pixelX + 1, pixelY + 1);
+                }
+            }
+
+            pixelOffset += dpi->pitch + dpi->width;
+            patternYPos++;
+            patternYPos %= patternYSpace;
+        }
+    }
 };
 
 class OpenGLDrawingEngine : public IDrawingEngine
@@ -138,6 +193,7 @@ private:
     OpenGLFramebuffer* _screenFramebuffer = nullptr;
     OpenGLFramebuffer* _scaleFramebuffer = nullptr;
     OpenGLFramebuffer* _smoothScaleFramebuffer = nullptr;
+    OpenGLRainDrawer _rainDrawer;
 
 public:
     SDL_Color Palette[256];
@@ -145,9 +201,10 @@ public:
 
     explicit OpenGLDrawingEngine(const std::shared_ptr<IUiContext>& uiContext)
         : _uiContext(uiContext)
+        , _drawingContext(new OpenGLDrawingContext(this))
+        , _rainDrawer(_drawingContext)
     {
         _window = (SDL_Window*)_uiContext->GetWindow();
-        _drawingContext = new OpenGLDrawingContext(this);
         _bitsDPI.DrawingEngine = this;
 #    ifdef __ENABLE_LIGHTFX__
         lightfx_set_available(false);
@@ -284,7 +341,8 @@ public:
 
     void PaintRain() override
     {
-        // Not implemented
+        _drawingContext->SetDPI(&_bitsDPI);
+        DrawRain(&_bitsDPI, &_rainDrawer);
     }
 
     std::string Screenshot() override
diff --git a/src/openrct2/drawing/Rain.h b/src/openrct2/drawing/Rain.h
index 591e4c59e6..dae0e61661 100644
--- a/src/openrct2/drawing/Rain.h
+++ b/src/openrct2/drawing/Rain.h
@@ -18,4 +18,14 @@ namespace OpenRCT2::Drawing
     interface IRainDrawer;
 }
 
+// clang-format off
+static constexpr const uint8_t RainPattern[] =
+{
+    32, 32, 0, 12, 0, 14, 0, 16, 255, 0, 255, 0, 255, 0, 255, 0, 255,
+    0, 255, 0, 255, 0, 255, 0, 255, 0, 255, 0, 255, 0, 255, 0, 255, 0,
+    255, 0, 255, 0, 255, 0, 255, 0, 255, 0, 255, 0, 255, 0, 255, 0, 255,
+    0, 255, 0, 255, 0, 255, 0, 255, 0, 255, 0, 255, 0, 255, 0, 0, 0
+};
+// clang-format on
+
 void DrawRain(rct_drawpixelinfo* dpi, OpenRCT2::Drawing::IRainDrawer* rainDrawer);
diff --git a/src/openrct2/drawing/X8DrawingEngine.cpp b/src/openrct2/drawing/X8DrawingEngine.cpp
index 6569f5bbe8..555cc548e3 100644
--- a/src/openrct2/drawing/X8DrawingEngine.cpp
+++ b/src/openrct2/drawing/X8DrawingEngine.cpp
@@ -47,16 +47,6 @@ void X8RainDrawer::SetDPI(rct_drawpixelinfo* dpi)
 
 void X8RainDrawer::Draw(int32_t x, int32_t y, int32_t width, int32_t height, int32_t xStart, int32_t yStart)
 {
-    // clang-format off
-    static constexpr const uint8_t RainPattern[] =
-    {
-        32, 32, 0, 12, 0, 14, 0, 16, 255, 0, 255, 0, 255, 0, 255, 0, 255,
-        0, 255, 0, 255, 0, 255, 0, 255, 0, 255, 0, 255, 0, 255, 0, 255, 0,
-        255, 0, 255, 0, 255, 0, 255, 0, 255, 0, 255, 0, 255, 0, 255, 0, 255,
-        0, 255, 0, 255, 0, 255, 0, 255, 0, 255, 0, 255, 0, 255, 0, 0, 0
-    };
-    // clang-format on
-
     const uint8_t* pattern = RainPattern;
     uint8_t patternXSpace = *pattern++;
     uint8_t patternYSpace = *pattern++;