Renderer: Adjust source rectangle when crop would draw off screen

This prevents us from requiring an oversized and/or negative viewport by
shrinking the source rectangle instead.

Source/Core/VideoBackends/D3D/Render.cpp

@@ -338,12 +338,14 @@ void Renderer::RenderXFBToScreen(const AbstractTexture* texture, const MathUtil:
   // Render to staging texture which is double the width of the backbuffer
   SetAndClearFramebuffer(m_3d_vision_framebuffer.get());
 
-  const auto target_rc = GetTargetRectangle();
+  auto adjusted_rc = rc;
-  m_post_processor->BlitFromTexture(target_rc, rc, texture, 0);
+  auto target_rc = GetTargetRectangle();
+  AdjustRectanglesToFitBounds(&target_rc, &adjusted_rc, m_backbuffer_width, m_backbuffer_height);
+  m_post_processor->BlitFromTexture(target_rc, adjusted_rc, texture, 0);
   m_post_processor->BlitFromTexture(
       MathUtil::Rectangle<int>(target_rc.left + m_backbuffer_width, target_rc.top,
                                target_rc.right + m_backbuffer_width, target_rc.bottom),
-      rc, texture, 1);
+      adjusted_rc, texture, 1);
 
   // Copy the left eye to the backbuffer, if Nvidia 3D Vision is enabled it should
   // recognize the signature and automatically include the right eye frame.

Source/Core/VideoBackends/OGL/Render.cpp

@@ -984,13 +984,15 @@ void Renderer::RenderXFBToScreen(const AbstractTexture* texture, const MathUtil:
   if (g_ActiveConfig.stereo_mode != StereoMode::QuadBuffer)
     return ::Renderer::RenderXFBToScreen(texture, rc);
 
-  const auto target_rc = GetTargetRectangle();
+  auto adjusted_rc = rc;
+  auto target_rc = GetTargetRectangle();
+  AdjustRectanglesToFitBounds(&target_rc, &adjusted_rc, m_backbuffer_width, m_backbuffer_height);
 
   glDrawBuffer(GL_BACK_LEFT);
-  m_post_processor->BlitFromTexture(target_rc, rc, texture, 0);
+  m_post_processor->BlitFromTexture(target_rc, adjusted_rc, texture, 0);
 
   glDrawBuffer(GL_BACK_RIGHT);
-  m_post_processor->BlitFromTexture(target_rc, rc, texture, 1);
+  m_post_processor->BlitFromTexture(target_rc, adjusted_rc, texture, 1);
 
   glDrawBuffer(GL_BACK);
 }

Source/Core/VideoCommon/RenderBase.cpp

@@ -561,6 +561,40 @@ float Renderer::CalculateDrawAspectRatio() const
   }
 }
 
+void Renderer::AdjustRectanglesToFitBounds(MathUtil::Rectangle<int>* target_rect,
+                                           MathUtil::Rectangle<int>* source_rect, int fb_width,
+                                           int fb_height)
+{
+  const int orig_target_width = target_rect->GetWidth();
+  const int orig_target_height = target_rect->GetHeight();
+  const int orig_source_width = source_rect->GetWidth();
+  const int orig_source_height = source_rect->GetHeight();
+  if (target_rect->left < 0)
+  {
+    const int offset = -target_rect->left;
+    target_rect->left = 0;
+    source_rect->left += offset * orig_source_width / orig_target_width;
+  }
+  if (target_rect->right > fb_width)
+  {
+    const int offset = target_rect->right - fb_width;
+    target_rect->right -= offset;
+    source_rect->right -= offset * orig_source_width / orig_target_width;
+  }
+  if (target_rect->top < 0)
+  {
+    const int offset = -target_rect->top;
+    target_rect->top = 0;
+    source_rect->top += offset * orig_source_height / orig_target_height;
+  }
+  if (target_rect->bottom > fb_height)
+  {
+    const int offset = target_rect->bottom - fb_height;
+    target_rect->right -= offset;
+    source_rect->right -= offset * orig_source_height / orig_target_height;
+  }
+}
+
 bool Renderer::IsHeadless() const
 {
   return true;
@@ -1287,19 +1321,21 @@ void Renderer::Swap(u32 xfb_addr, u32 fb_width, u32 fb_stride, u32 fb_height, u6
 
 void Renderer::RenderXFBToScreen(const AbstractTexture* texture, const MathUtil::Rectangle<int>& rc)
 {
-  const auto target_rc = GetTargetRectangle();
+  auto adjusted_rc = rc;
+  auto target_rc = GetTargetRectangle();
+  AdjustRectanglesToFitBounds(&target_rc, &adjusted_rc, m_backbuffer_width, m_backbuffer_height);
   if (g_ActiveConfig.stereo_mode == StereoMode::SBS ||
       g_ActiveConfig.stereo_mode == StereoMode::TAB)
   {
     MathUtil::Rectangle<int> left_rc, right_rc;
     std::tie(left_rc, right_rc) = ConvertStereoRectangle(target_rc);
 
-    m_post_processor->BlitFromTexture(left_rc, rc, texture, 0);
+    m_post_processor->BlitFromTexture(left_rc, adjusted_rc, texture, 0);
-    m_post_processor->BlitFromTexture(right_rc, rc, texture, 1);
+    m_post_processor->BlitFromTexture(right_rc, adjusted_rc, texture, 1);
   }
   else
   {
-    m_post_processor->BlitFromTexture(target_rc, rc, texture, 0);
+    m_post_processor->BlitFromTexture(target_rc, adjusted_rc, texture, 0);
   }
 }
 

Source/Core/VideoCommon/RenderBase.h

@@ -171,6 +171,13 @@ public:
   const MathUtil::Rectangle<int>& GetTargetRectangle() const { return m_target_rectangle; }
   float CalculateDrawAspectRatio() const;
 
+  // Crops the target rectangle to the framebuffer dimensions, reducing the size of the source
+  // rectangle if it is greater. Works even if the source and target rectangles don't have a
+  // 1:1 pixel mapping, scaling as appropriate.
+  void AdjustRectanglesToFitBounds(MathUtil::Rectangle<int>* target_rect,
+                                   MathUtil::Rectangle<int>* source_rect, int fb_width,
+                                   int fb_height);
+
   std::tuple<float, float> ScaleToDisplayAspectRatio(int width, int height) const;
   void UpdateDrawRectangle();