GPU: Prevent potential overflow in CRTC visible area calculation

src/core/gpu.cpp

@@ -568,6 +568,14 @@ void GPU::UpdateCRTCDisplayParameters()
         cs.vertical_visible_end = vertical_display_end;
         break;
     }
+    cs.horizontal_visible_start =
+      std::clamp<u16>(cs.horizontal_visible_start, PAL_HORIZONTAL_ACTIVE_START, PAL_HORIZONTAL_ACTIVE_END);
+    cs.horizontal_visible_end =
+      std::clamp<u16>(cs.horizontal_visible_end, cs.horizontal_visible_start, PAL_HORIZONTAL_ACTIVE_END);
+    cs.vertical_visible_start =
+      std::clamp<u16>(cs.vertical_visible_start, PAL_VERTICAL_ACTIVE_START, PAL_VERTICAL_ACTIVE_END);
+    cs.vertical_visible_end =
+      std::clamp<u16>(cs.vertical_visible_end, cs.vertical_visible_start, PAL_VERTICAL_ACTIVE_END);
   }
   else
   {
@@ -597,6 +605,14 @@ void GPU::UpdateCRTCDisplayParameters()
         cs.vertical_visible_end = vertical_display_end;
         break;
     }
+    cs.horizontal_visible_start =
+      std::clamp<u16>(cs.horizontal_visible_start, NTSC_HORIZONTAL_ACTIVE_START, NTSC_HORIZONTAL_ACTIVE_END);
+    cs.horizontal_visible_end =
+      std::clamp<u16>(cs.horizontal_visible_end, cs.horizontal_visible_start, NTSC_HORIZONTAL_ACTIVE_END);
+    cs.vertical_visible_start =
+      std::clamp<u16>(cs.vertical_visible_start, NTSC_VERTICAL_ACTIVE_START, NTSC_VERTICAL_ACTIVE_END);
+    cs.vertical_visible_end =
+      std::clamp<u16>(cs.vertical_visible_end, cs.vertical_visible_start, NTSC_VERTICAL_ACTIVE_END);
   }
 
   // If force-progressive is enabled, we only double the height in 480i mode. This way non-interleaved 480i framebuffers

src/core/gpu.h

@@ -497,6 +497,7 @@ protected:
     u16 display_vram_width;
     u16 display_vram_height;
 
+    // Visible range of the screen, in GPU ticks/lines. Clamped to lie within the active video region.
     u16 horizontal_visible_start;
     u16 horizontal_visible_end;
     u16 vertical_visible_start;