From 3d0c23597d1d8fdb22921e6c273e7ccd99cbd77f Mon Sep 17 00:00:00 2001
From: Matthias Clasen <mclasen@redhat.com>
Date: Thu, 15 Jul 2021 16:40:13 -0400
Subject: [PATCH 1/2] ngl: Handle negative scales

Scale factors can be negative, but we were not
looking out for that, triggering an assertion when
trying to create a render target with negative
width of height. Avoid that.

Fixes: #4096
---
 gsk/ngl/gsknglrenderjob.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/gsk/ngl/gsknglrenderjob.c b/gsk/ngl/gsknglrenderjob.c
index 3e823dedab..02f8bcc4b8 100644
--- a/gsk/ngl/gsknglrenderjob.c
+++ b/gsk/ngl/gsknglrenderjob.c
@@ -3573,19 +3573,23 @@ gsk_ngl_render_job_visit_node_with_offscreen (GskNglRenderJob       *job,
   {
     int max_texture_size = job->command_queue->max_texture_size;
 
-    scaled_width = ceilf (offscreen->bounds->size.width * job->scale_x);
+    scaled_width = ceilf (offscreen->bounds->size.width * fabs (job->scale_x));
     if (scaled_width > max_texture_size)
       {
         downscale_x = (float)max_texture_size / scaled_width;
         scaled_width = max_texture_size;
       }
+    if (job->scale_x < 0)
+      downscale_x = -downscale_x;
 
-    scaled_height = ceilf (offscreen->bounds->size.height * job->scale_y);
+    scaled_height = ceilf (offscreen->bounds->size.height * fabs (job->scale_y));
     if (scaled_height > max_texture_size)
       {
         downscale_y = (float)max_texture_size / scaled_height;
         scaled_height = max_texture_size;
       }
+    if (job->scale_y < 0)
+      downscale_y = -downscale_y;
   }
 
   GskNglRenderTarget *render_target;

From 14df31b5090372a612fac6996bfb864dfac7f507 Mon Sep 17 00:00:00 2001
From: Benjamin Otte <otte@redhat.com>
Date: Thu, 15 Jul 2021 23:33:54 +0200
Subject: [PATCH 2/2] testsuite: Add test for crasher

Test for the crasher in !4096
---
 .../compare/scale-textures-negative-ngl.node  |  48 ++++++++++++++++++
 .../compare/scale-textures-negative-ngl.png   | Bin 0 -> 265 bytes
 testsuite/gsk/meson.build                     |   1 +
 3 files changed, 49 insertions(+)
 create mode 100644 testsuite/gsk/compare/scale-textures-negative-ngl.node
 create mode 100644 testsuite/gsk/compare/scale-textures-negative-ngl.png

diff --git a/testsuite/gsk/compare/scale-textures-negative-ngl.node b/testsuite/gsk/compare/scale-textures-negative-ngl.node
new file mode 100644
index 0000000000..fbf1d8205e
--- /dev/null
+++ b/testsuite/gsk/compare/scale-textures-negative-ngl.node
@@ -0,0 +1,48 @@
+transform {
+  transform: scale(1, 1);
+  child: opacity {
+    opacity: 0.6;
+    child: container {
+      texture {
+        bounds: 0 0 50 50;
+        texture: url("data:,<svg width='50' height='50'><rect x='25' y='25' width='25' height='25' fill='red'/></svg>");
+      }
+    }
+  }
+}
+transform {
+  transform: scale(1, -1);
+  child: opacity {
+    opacity: 0.6;
+    child: container {
+      texture {
+        bounds: 0 0 50 50;
+        texture: url("data:,<svg width='50' height='50'><rect x='25' y='25' width='25' height='25' fill='lime'/></svg>");
+      }
+    }
+  }
+}
+transform {
+  transform: scale(-1, -1);
+  child: opacity {
+    opacity: 0.6;
+    child: container {
+      texture {
+        bounds: 0 0 50 50;
+        texture: url("data:,<svg width='50' height='50'><rect x='25' y='25' width='25' height='25' fill='blue'/></svg>");
+      }
+    }
+  }
+}
+transform {
+  transform: scale(-1, 1);
+  child: opacity {
+    opacity: 0.6;
+    child: container {
+      texture {
+        bounds: 0 0 50 50;
+        texture: url("data:,<svg width='50' height='50'><rect x='25' y='25' width='25' height='25' fill='yellow'/></svg>");
+      }
+    }
+  }
+}
diff --git a/testsuite/gsk/compare/scale-textures-negative-ngl.png b/testsuite/gsk/compare/scale-textures-negative-ngl.png
new file mode 100644
index 0000000000000000000000000000000000000000..8624e6c403dc52515a4c822b6d18493131912346
GIT binary patch
literal 265
zcmeAS@N?(olHy`uVBq!ia0vp^DIm<j1|$m}O$`B3Y)RhkE)4%caKYZ?lYt`pJY5_^
zD(1Ys+sMgm$iw1jd3M>dkk?lPI_5vEU&h$Dts&a@xAF0{-+xMr-zfeQzWy@%k6s1C
zrXw6e${syLGnjxjp@aI3-&l(mWuMhu7XE!kT&;{_5=*C`irWMU;u+7lXZdqXmXc8g
Pd6B`>)z4*}Q$iB}eY#M`

literal 0
HcmV?d00001

diff --git a/testsuite/gsk/meson.build b/testsuite/gsk/meson.build
index edb06ad154..c3f674599e 100644
--- a/testsuite/gsk/meson.build
+++ b/testsuite/gsk/meson.build
@@ -56,6 +56,7 @@ compare_render_tests = [
   'outset_shadow_rounded_top',
   'outset_shadow_simple',
   'scaled-cairo',
+  'scale-textures-negative-ngl',
   'shadow-in-opacity',
   'texture-url',
   'color-matrix-identity',