From 8c6cb877eb5a968f83d420d9825fc1bdcdb81e5f Mon Sep 17 00:00:00 2001
From: Connor McLaughlin <stenzek@gmail.com>
Date: Mon, 27 Apr 2020 21:49:34 +1000
Subject: [PATCH] GPU: Disable display when CRTC configuration is invalid

---
 src/core/gpu.cpp           | 31 ++++++++++++++++++-------------
 src/core/gpu.h             |  6 ++++++
 src/core/gpu_hw_d3d11.cpp  |  2 +-
 src/core/gpu_hw_opengl.cpp |  2 +-
 src/core/gpu_sw.cpp        |  2 +-
 5 files changed, 27 insertions(+), 16 deletions(-)

diff --git a/src/core/gpu.cpp b/src/core/gpu.cpp
index d76b904ff..41c226598 100644
--- a/src/core/gpu.cpp
+++ b/src/core/gpu.cpp
@@ -517,19 +517,21 @@ void GPU::UpdateCRTCDisplayParameters()
 
   if (horizontal_display_end <= cs.horizontal_active_end)
   {
-    cs.display_vram_width =
-      std::max<u16>((((horizontal_display_end - std::max(horizontal_display_start, cs.horizontal_active_start)) +
-                      (cs.dot_clock_divider - 1)) /
-                     cs.dot_clock_divider),
-                    1u);
+    cs.display_vram_width = std::max<u16>(
+      (((horizontal_display_end -
+         std::min(horizontal_display_end, std::max(horizontal_display_start, cs.horizontal_active_start))) +
+        (cs.dot_clock_divider - 1)) /
+       cs.dot_clock_divider),
+      1u);
   }
   else
   {
-    cs.display_vram_width =
-      std::max<u16>((((cs.horizontal_active_end - std::max(horizontal_display_start, cs.horizontal_active_start)) +
-                      (cs.dot_clock_divider - 1)) /
-                     cs.dot_clock_divider),
-                    1u);
+    cs.display_vram_width = std::max<u16>(
+      (((cs.horizontal_active_end -
+         std::min(cs.horizontal_active_end, std::max(horizontal_display_start, cs.horizontal_active_start))) +
+        (cs.dot_clock_divider - 1)) /
+       cs.dot_clock_divider),
+      1u);
   }
 
   if (vertical_display_start >= cs.vertical_active_start)
@@ -545,13 +547,16 @@ void GPU::UpdateCRTCDisplayParameters()
 
   if (vertical_display_end <= cs.vertical_active_end)
   {
-    cs.display_vram_height = (vertical_display_end - std::max(vertical_display_start, cs.vertical_active_start))
+    cs.display_vram_height = (vertical_display_end - std::min(vertical_display_end, std::max(vertical_display_start,
+                                                                                             cs.vertical_active_start)))
                              << height_shift;
   }
   else
   {
-    cs.display_vram_height = (cs.vertical_active_end - std::max(vertical_display_start, cs.vertical_active_start))
-                             << height_shift;
+    cs.display_vram_height =
+      (cs.vertical_active_end -
+       std::min(vertical_display_end, std::max(vertical_display_start, cs.vertical_active_start)))
+      << height_shift;
   }
 }
 
diff --git a/src/core/gpu.h b/src/core/gpu.h
index fdc7b123e..d43503679 100644
--- a/src/core/gpu.h
+++ b/src/core/gpu.h
@@ -334,6 +334,12 @@ protected:
   // Ticks for hblank/vblank.
   void Execute(TickCount ticks);
 
+  /// Returns false if the DAC is loading any data from VRAM.
+  ALWAYS_INLINE bool IsDisplayDisabled() const
+  {
+    return m_GPUSTAT.display_disable || m_crtc_state.display_vram_width == 0 || m_crtc_state.display_vram_height == 0;
+  }
+
   /// Returns true if scanout should be interlaced.
   ALWAYS_INLINE bool IsInterlacedDisplayEnabled() const { return (!m_force_progressive_scan) & m_GPUSTAT.In480iMode(); }
 
diff --git a/src/core/gpu_hw_d3d11.cpp b/src/core/gpu_hw_d3d11.cpp
index 017697d46..ee65bc35c 100644
--- a/src/core/gpu_hw_d3d11.cpp
+++ b/src/core/gpu_hw_d3d11.cpp
@@ -552,7 +552,7 @@ void GPU_HW_D3D11::UpdateDisplay()
     const u32 scaled_display_height = display_height * m_resolution_scale;
     const bool interlaced = IsInterlacedDisplayEnabled();
 
-    if (m_GPUSTAT.display_disable)
+    if (IsDisplayDisabled())
     {
       m_host_display->ClearDisplayTexture();
     }
diff --git a/src/core/gpu_hw_opengl.cpp b/src/core/gpu_hw_opengl.cpp
index dc7ba8c1f..f2e546927 100644
--- a/src/core/gpu_hw_opengl.cpp
+++ b/src/core/gpu_hw_opengl.cpp
@@ -544,7 +544,7 @@ void GPU_HW_OpenGL::UpdateDisplay()
     const u32 scaled_display_height = display_height * m_resolution_scale;
     const bool interlaced = IsInterlacedDisplayEnabled();
 
-    if (m_GPUSTAT.display_disable)
+    if (IsDisplayDisabled())
     {
       m_host_display->ClearDisplayTexture();
     }
diff --git a/src/core/gpu_sw.cpp b/src/core/gpu_sw.cpp
index 9bda22730..7e5c44809 100644
--- a/src/core/gpu_sw.cpp
+++ b/src/core/gpu_sw.cpp
@@ -144,7 +144,7 @@ void GPU_SW::UpdateDisplay()
 
   if (!m_system->GetSettings().debugging.show_vram)
   {
-    if (m_GPUSTAT.display_disable)
+    if (IsDisplayDisabled())
     {
       m_host_display->ClearDisplayTexture();
       return;