Fix #6647: Prevent changelog window from painting lines out of view. (#7611)

distribution/changelog.txt

@@ -18,6 +18,7 @@
 - Fix: [#5210] Default system dialog not accessible from saving landscape window.
 - Fix: [#6134] Scenarios incorrectly categorised when using Polish version of RCT2.
 - Fix: [#6141] CSS50.dat is never loaded.
+- Fix: [#6647] Changelog window causes FPS drop.
 - Fix: [#6938] Banner do not correctly capitalise non-ASCII characters.
 - Fix: [#7176] Mechanics sometimes fall down from rides.
 - Fix: [#7303] Visual glitch with virtual floor near map edges.

src/openrct2-ui/windows/Changelog.cpp

@@ -170,7 +170,9 @@ static void window_changelog_scrollgetsize(
     [[maybe_unused]] rct_window * w, [[maybe_unused]] sint32 scrollIndex, sint32 * width, sint32 * height)
 {
     *width = _changelogLongestLineWidth + 4;
-    *height = (sint32)(_changelogLines.size() * 11);
+
+    const sint32 lineHeight = font_get_line_height(gCurrentFontSpriteBase);
+    *height = (sint32)(_changelogLines.size() * lineHeight);
 }
 
 static void window_changelog_invalidate(rct_window *w)
@@ -196,12 +198,17 @@ static void window_changelog_scrollpaint(rct_window * w, rct_drawpixelinfo * dpi
     gCurrentFontFlags = 0;
     gCurrentFontSpriteBase = FONT_SPRITE_BASE_MEDIUM;
 
+    const sint32 lineHeight = font_get_line_height(gCurrentFontSpriteBase);
+
     sint32 x = 3;
-    sint32 y = 3;
+    sint32 y = 3 - lineHeight;
     for (auto line : _changelogLines)
     {
+        y += lineHeight;
+        if (y + lineHeight < dpi->y || y >= dpi->y + dpi->height)
+            continue;
+
         gfx_draw_string(dpi, (char *)line, w->colours[0], x, y);
-        y += 11;
     }
 }