Re-enable pdf tests with gradients and add poppler-based reference images

This freezes the current (buggy) poppler result in the test suite
so that we will notice any future regressions.

12 files changed, 51 insertions, 8 deletions

diff --git a/test/README b/test/README
index 840e1addb..a603e9887 100644
--- a/test/README
+++ b/test/README
@@ -94,3 +94,50 @@ message:
 
 	All XX tests passed
 
+Some notes on limitations in poppler
+------------------------------------
+One of the difficulties of our current test infrastructure is that we
+rely on external tools to convert cairo's vector output (PDF,
+PostScript, and SVG), into an image that can be used for the image
+comparison. This means that any bugs in that conversion tool will
+result in false negatives in the test suite.
+
+We've identified several such bugs in the poppler library which is
+used to convert PDF to an image. This is particularly discouraging
+because 1) poppler is free software that will be used by *many* cairo
+users, and 2) poppler calls into cairo for its rendering so it should
+be able to do a 100% faithful conversion.
+
+So we have an interest in ensuring that these poppler bugs get fixed
+sooner rather than later. As such, we're trying to be good citizens by
+reporting all such poppler bugs that we identify to the poppler
+bugzilla. Here's a tracking bug explaining the situation:
+
+	Poppler does not yet handle everything in the cairo test suite
+	https://bugs.freedesktop.org/show_bug.cgi?id=12143
+
+Here's the rule: If a cairo-pdf test reports a failure, but viewing
+the resulting PDF file with acroread suggests that the PDF itself is
+correct, then there's likely a bug in poppler. In this case, we can
+simply report the poppler bug, (making it block 12143 above), post the
+PDF result from the test suite, and list the bug in this file. Once
+we've done this, we can capture poppler's buggy output as a
+pdf-specific reference image so that the test suite will regard the
+test as passing, (and we'll ensure there is no regression).
+
+Once the poppler bug gets fixed, the test suite will start reporting a
+false negative again, and this will be easy to fix by simply removing
+the pdf-specific reference image.
+
+Here are the reported poppler bugs and the tests they affect:
+
+Poppler doesn't correctly handle gradients with transparency
+https://bugs.freedesktop.org/show_bug.cgi?id=12144
+--------------------------------------------------
+gradient-alpha
+linear-gradient
+trap-clip
+linear-gradient
+linear-gradient-reflect
+
+
diff --git a/test/gradient-alpha-pdf-argb32-ref.png b/test/gradient-alpha-pdf-argb32-ref.png
new file mode 100644
index 000000000..bf9c69ab5
--- /dev/null
+++ b/test/gradient-alpha-pdf-argb32-ref.png
diff --git a/test/gradient-alpha-pdf-rgb24-ref.png b/test/gradient-alpha-pdf-rgb24-ref.png
new file mode 100644
index 000000000..798527384
--- /dev/null
+++ b/test/gradient-alpha-pdf-rgb24-ref.png
diff --git a/test/gradient-alpha.c b/test/gradient-alpha.c
index 6646aec41..6b762476d 100644
--- a/test/gradient-alpha.c
+++ b/test/gradient-alpha.c
@@ -29,8 +29,7 @@ static cairo_test_draw_function_t draw;
 
 cairo_test_t test = {
     "gradient-alpha",
-    "Tests drawing of a gradient with various alpha values in the color stops\n"
-    "PDF backend will not be tested due to limitations in poppler.",
+    "Tests drawing of a gradient with various alpha values in the color stops\n",
     10, 10,
     draw
 };
diff --git a/test/linear-gradient-pdf-ref.png b/test/linear-gradient-pdf-ref.png
new file mode 100644
index 000000000..ede7c9011
--- /dev/null
+++ b/test/linear-gradient-pdf-ref.png
diff --git a/test/linear-gradient-reflect-pdf-argb32-ref.png b/test/linear-gradient-reflect-pdf-argb32-ref.png
new file mode 100644
index 000000000..46e1c0f0e
--- /dev/null
+++ b/test/linear-gradient-reflect-pdf-argb32-ref.png
diff --git a/test/linear-gradient-reflect-pdf-rgb24-ref.png b/test/linear-gradient-reflect-pdf-rgb24-ref.png
new file mode 100644
index 000000000..46e1c0f0e
--- /dev/null
+++ b/test/linear-gradient-reflect-pdf-rgb24-ref.png
diff --git a/test/linear-gradient.c b/test/linear-gradient.c
index 71a57f671..3dad477c7 100644
--- a/test/linear-gradient.c
+++ b/test/linear-gradient.c
@@ -58,8 +58,7 @@ static cairo_test_draw_function_t draw;
 
 cairo_test_t test = {
     "linear-gradient",
-    "Tests the drawing of linear gradients\n"
-    "PDF backend will not be tested due to limitations in poppler.",
+    "Tests the drawing of linear gradients\n",
     WIDTH, HEIGHT,
     draw
 };
diff --git a/test/text-pattern.c b/test/text-pattern.c
index 99ac9fd95..15a909df0 100644
--- a/test/text-pattern.c
+++ b/test/text-pattern.c
@@ -32,8 +32,7 @@ static cairo_test_draw_function_t draw;
 
 cairo_test_t test = {
     "text-pattern",
-    "Patterned Text\n"
-    "PDF backend will not be tested due to limitations in poppler.",
+    "Patterned Text\n",
     IMAGE_WIDTH, IMAGE_HEIGHT,
     draw
 };
diff --git a/test/trap-clip-pdf-argb32-ref.png b/test/trap-clip-pdf-argb32-ref.png
new file mode 100644
index 000000000..c3ee9971a
--- /dev/null
+++ b/test/trap-clip-pdf-argb32-ref.png
diff --git a/test/trap-clip-pdf-rgb24-ref.png b/test/trap-clip-pdf-rgb24-ref.png
new file mode 100644
index 000000000..f787011cb
--- /dev/null
+++ b/test/trap-clip-pdf-rgb24-ref.png
diff --git a/test/trap-clip.c b/test/trap-clip.c
index a33985f62..3712c9024 100644
--- a/test/trap-clip.c
+++ b/test/trap-clip.c
@@ -168,8 +168,7 @@ static cairo_test_draw_function_t draw;
 
 cairo_test_t test = {
     "trap-clip",
-    "Trapezoid clipping\n"
-    "PDF backend will not be tested due to limitations in poppler.",
+    "Trapezoid clipping\n",
     IMAGE_WIDTH, IMAGE_HEIGHT,
     draw
 };