From 77a2cd4d8dbf108ac36b9866b50257fbb057b719 Mon Sep 17 00:00:00 2001
From: Matthias Clasen <mclasen@redhat.com>
Date: Mon, 4 Mar 2024 14:49:01 -0500
Subject: [PATCH] gsk: Fix mis-scaled text rendering

This was happening when rotated text was partially redrawn.

A test that failed before this change is included.

Fixes: #6504
---
 gsk/gpu/gskgpunodeprocessor.c                  |  11 +++++++----
 .../compare/offscreen-forced-downscale.node    |  17 +++++++++++++++++
 .../gsk/compare/offscreen-forced-downscale.png | Bin 0 -> 391 bytes
 testsuite/gsk/meson.build                      |   1 +
 4 files changed, 25 insertions(+), 4 deletions(-)
 create mode 100644 testsuite/gsk/compare/offscreen-forced-downscale.node
 create mode 100644 testsuite/gsk/compare/offscreen-forced-downscale.png

diff --git a/gsk/gpu/gskgpunodeprocessor.c b/gsk/gpu/gskgpunodeprocessor.c
index b4be4ac605..793842ebe6 100644
--- a/gsk/gpu/gskgpunodeprocessor.c
+++ b/gsk/gpu/gskgpunodeprocessor.c
@@ -1649,10 +1649,13 @@ gsk_gpu_node_processor_add_transform_node (GskGpuNodeProcessor *self,
 
         extract_scale_from_transform (self->modelview, &scale_x, &scale_y);
 
-        old_pixels = graphene_vec2_get_x (&old_scale) * graphene_vec2_get_y (&old_scale) *
-                     old_clip.rect.bounds.size.width * old_clip.rect.bounds.size.height;
-        new_pixels = scale_x * scale_y * self->clip.rect.bounds.size.width * self->clip.rect.bounds.size.height;
-        if (new_pixels > 2 * old_pixels)
+        old_pixels = MAX (graphene_vec2_get_x (&old_scale) * old_clip.rect.bounds.size.width,
+                          graphene_vec2_get_y (&old_scale) * old_clip.rect.bounds.size.height);
+        new_pixels = MAX (scale_x * self->clip.rect.bounds.size.width,
+                          scale_y * self->clip.rect.bounds.size.height);
+
+        /* Check that our offscreen doesn't get too big.  1.5 ~ sqrt(2) */
+        if (new_pixels > 1.5 * old_pixels)
           {
             float forced_downscale = 2 * old_pixels / new_pixels;
             scale_x *= forced_downscale;
diff --git a/testsuite/gsk/compare/offscreen-forced-downscale.node b/testsuite/gsk/compare/offscreen-forced-downscale.node
new file mode 100644
index 0000000000..bc62728c9c
--- /dev/null
+++ b/testsuite/gsk/compare/offscreen-forced-downscale.node
@@ -0,0 +1,17 @@
+color {
+  bounds: -10 -10 20 120;
+  color: rgb(255,255,255);
+}
+transform {
+  transform: rotate(45);
+  child: transform {
+    transform: rotate(45);
+    child: shadow {
+      shadows: rgb(0,0,0) 0 1;
+      child: color {
+        bounds: 0 0 100 1;
+        color: rgb(255,0,0);
+      }
+    }
+  }
+}
diff --git a/testsuite/gsk/compare/offscreen-forced-downscale.png b/testsuite/gsk/compare/offscreen-forced-downscale.png
new file mode 100644
index 0000000000000000000000000000000000000000..c4dd21a0a156fce067d167a4cb41eb1c94c911c4
GIT binary patch
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literal 0
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diff --git a/testsuite/gsk/meson.build b/testsuite/gsk/meson.build
index 400824aad4..5377cbec23 100644
--- a/testsuite/gsk/meson.build
+++ b/testsuite/gsk/meson.build
@@ -104,6 +104,7 @@ compare_render_tests = [
   'mask-texture-color-alpha',
   'mipmap-generation-later',
   'nested-rounded-clips',
+  'offscreen-forced-downscale',
   'offscreen-fractional-translate-nogl',
   'offscreen-pixel-alignment-nogl-nocairo',
   'offscreen-pixel-alignment2',