From 23c9e0a8b2ca587b093cb8f63d73a6632be6cf98 Mon Sep 17 00:00:00 2001
From: Ben Harris <bjh21@bjh21.me.uk>
Date: Thu, 29 Dec 2022 00:07:55 +0000
Subject: [PATCH] Pattern: Clip clues to their proper rectangles

Since the drawing API offers no guarantees about where text drawing
might have effects, it's unsafe to erase text other than by wiping the
clipping rectangle that was in effect when it was drawn.  In practice,
this means that all variable (including colour) text should be drawn
with a narrow clipping rectangle.

It wasn't actually a practical problem that Pattern didn't clip its
clues, but I'll like to make its fonts less tiny, which will make it
more likely to need clipping in odd cases.

This also factors out some repeated computations in draw_numbers().
---
 pattern.c | 38 +++++++++++++++++++-------------------
 1 file changed, 19 insertions(+), 19 deletions(-)

diff --git a/pattern.c b/pattern.c
index afe1768..73cf12a 100644
--- a/pattern.c
+++ b/pattern.c
@@ -1760,19 +1760,24 @@ static void draw_numbers(
     int *rowdata = state->common->rowdata + state->common->rowsize * i;
     int nfit;
     int j;
+    int rx, ry, rw, rh;
 
-    if (erase) {
-        if (i < state->common->w) {
-            draw_rect(dr, TOCOORD(state->common->w, i), 0,
-                      TILE_SIZE, BORDER + TLBORDER(state->common->h) * TILE_SIZE,
-                      COL_BACKGROUND);
-        } else {
-            draw_rect(dr, 0, TOCOORD(state->common->h, i - state->common->w),
-                      BORDER + TLBORDER(state->common->w) * TILE_SIZE, TILE_SIZE,
-                      COL_BACKGROUND);
-        }
+    if (i < state->common->w) {
+        rx = TOCOORD(state->common->w, i);
+        ry = 0;
+        rw = TILE_SIZE;
+        rh = BORDER + TLBORDER(state->common->h) * TILE_SIZE;
+    } else {
+        rx = 0;
+        ry = TOCOORD(state->common->h, i - state->common->w);
+        rw = BORDER + TLBORDER(state->common->w) * TILE_SIZE;
+        rh = TILE_SIZE;
     }
 
+    clip(dr, rx, ry, rw, rh);
+    if (erase)
+        draw_rect(dr, rx, ry, rw, rh, COL_BACKGROUND);
+
     /*
      * Normally I space the numbers out by the same distance as the
      * tile size. However, if there are more numbers than available
@@ -1790,11 +1795,11 @@ static void draw_numbers(
         char str[80];
 
         if (i < state->common->w) {
-            x = TOCOORD(state->common->w, i);
+            x = rx;
             y = BORDER + TILE_SIZE * (TLBORDER(state->common->h)-1);
             y -= ((rowlen-j-1)*TILE_SIZE) * (TLBORDER(state->common->h)-1) / nfit;
         } else {
-            y = TOCOORD(state->common->h, i - state->common->w);
+            y = ry;
             x = BORDER + TILE_SIZE * (TLBORDER(state->common->w)-1);
             x -= ((rowlen-j-1)*TILE_SIZE) * (TLBORDER(state->common->w)-1) / nfit;
         }
@@ -1804,13 +1809,8 @@ static void draw_numbers(
                   TILE_SIZE/2, ALIGN_HCENTRE | ALIGN_VCENTRE, colour, str);
     }
 
-    if (i < state->common->w) {
-        draw_update(dr, TOCOORD(state->common->w, i), 0,
-                    TILE_SIZE, BORDER + TLBORDER(state->common->h) * TILE_SIZE);
-    } else {
-        draw_update(dr, 0, TOCOORD(state->common->h, i - state->common->w),
-                    BORDER + TLBORDER(state->common->w) * TILE_SIZE, TILE_SIZE);
-    }
+    unclip(dr);
+    draw_update(dr, rx, ry, rw, rh);
 }
 
 static void game_redraw(drawing *dr, game_drawstate *ds,