Bug 695040: prevent hang in path flattening

If the expansion of a transformation matrix is huge, the path flatness
becomes so small that even simple paths consist of millions of edges
which easily causes MuPDF to hang quite long for simple documents. One
solution for this is to limit the allowed flatness.

1 files changed, 10 insertions, 0 deletions

diff --git a/source/fitz/draw-device.c b/source/fitz/draw-device.c
index 3effa3a73..98b7990c4 100644
--- a/source/fitz/draw-device.c
+++ b/source/fitz/draw-device.c
@@ -256,6 +256,9 @@ fz_draw_fill_path(fz_device *devp, fz_path *path, int even_odd, const fz_matrix
         if (model == NULL)
                 model = fz_device_gray(dev->ctx);
 
+        if (flatness < 0.001f)
+                flatness = 0.001f;
+
         fz_reset_gel(dev->gel, &state->scissor);
         fz_flatten_fill_path(dev->gel, path, ctm, flatness);
         fz_sort_gel(dev->gel);
@@ -308,6 +311,8 @@ fz_draw_stroke_path(fz_device *devp, fz_path *path, fz_stroke_state *stroke, con
 
         if (linewidth * expansion < 0.1f)
                 linewidth = 1 / expansion;
+        if (flatness < 0.001f)
+                flatness = 0.001f;
 
         fz_reset_gel(dev->gel, &state->scissor);
         if (stroke->dash_len > 0)
@@ -358,6 +363,9 @@ fz_draw_clip_path(fz_device *devp, fz_path *path, const fz_rect *rect, int even_
         fz_colorspace *model;
         fz_context *ctx = dev->ctx;
 
+        if (flatness < 0.001f)
+                flatness = 0.001f;
+
         fz_reset_gel(dev->gel, &state->scissor);
         fz_flatten_fill_path(dev->gel, path, ctm, flatness);
         fz_sort_gel(dev->gel);
@@ -422,6 +430,8 @@ fz_draw_clip_stroke_path(fz_device *devp, fz_path *path, const fz_rect *rect, fz
 
         if (linewidth * expansion < 0.1f)
                 linewidth = 1 / expansion;
+        if (flatness < 0.001f)
+                flatness = 0.001f;
 
         fz_reset_gel(dev->gel, &state->scissor);
         if (stroke->dash_len > 0)