Sky: paint the full window width (#717)

The gradient quad's projection path does not preserve the outward
rounding of the Rect edge getters, which can leave the last window
column unpainted at some aspect ratios (visible as a black strip at the
screen edge that only sky sprites drew into). Overshoot the quad a few
virtual pixels past both edges; the excess clips at the window.

Co-authored-by: MegaMech <MegaMech@users.noreply.github.com>

1 files changed, 12 insertions, 9 deletions

diff --git a/src/engine/sky/Sky.cpp b/src/engine/sky/Sky.cpp
index 5e1afc1a7..d9a9a1112 100644
--- a/src/engine/sky/Sky.cpp
+++ b/src/engine/sky/Sky.cpp
@@ -184,15 +184,18 @@ void Sky::Draw(ScreenContext* screen) { // func_802A4A0C(Vtx* vtx, ScreenContext
     this->SetColours(vtx); //func_802A450C(vtx);
     // Widescreen skybox
     // Note that this is the correct fit for each screen due to how the viewport works
-    vtx[0].v.ob[0] = OTRGetRectDimensionFromRightEdge(SCREEN_WIDTH);
-    vtx[1].v.ob[0] = OTRGetRectDimensionFromRightEdge(SCREEN_WIDTH);
-    vtx[2].v.ob[0] = OTRGetRectDimensionFromLeftEdge(0);
-    vtx[3].v.ob[0] = OTRGetRectDimensionFromLeftEdge(0);
-
-    vtx[4].v.ob[0] = OTRGetRectDimensionFromRightEdge(SCREEN_WIDTH);
-    vtx[5].v.ob[0] = OTRGetRectDimensionFromRightEdge(SCREEN_WIDTH);
-    vtx[6].v.ob[0] = OTRGetRectDimensionFromLeftEdge(0);
-    vtx[7].v.ob[0] = OTRGetRectDimensionFromLeftEdge(0);
+    // +/-8: overshoot the gradient past both edges; this quad's projection
+    // path does not preserve the Rect getters' outward rounding, which left
+    // the last window column unpainted at some aspect ratios.
+    vtx[0].v.ob[0] = OTRGetRectDimensionFromRightEdge(SCREEN_WIDTH) + 8;
+    vtx[1].v.ob[0] = OTRGetRectDimensionFromRightEdge(SCREEN_WIDTH) + 8;
+    vtx[2].v.ob[0] = OTRGetRectDimensionFromLeftEdge(0) - 8;
+    vtx[3].v.ob[0] = OTRGetRectDimensionFromLeftEdge(0) - 8;
+
+    vtx[4].v.ob[0] = OTRGetRectDimensionFromRightEdge(SCREEN_WIDTH) + 8;
+    vtx[5].v.ob[0] = OTRGetRectDimensionFromRightEdge(SCREEN_WIDTH) + 8;
+    vtx[6].v.ob[0] = OTRGetRectDimensionFromLeftEdge(0) - 8;
+    vtx[7].v.ob[0] = OTRGetRectDimensionFromLeftEdge(0) - 8;
 
     sp5C[0] = 0.0f;
     sp5C[1] = 0.0f;