From 06b375aee999220ce294c22fa50a3040c19d5492 Mon Sep 17 00:00:00 2001
From: Chris Wilson <chris@chris-wilson.co.uk>
Date: Fri, 29 Feb 2008 11:55:01 +0000
Subject: [PATCH] [cairo-png] Use cairo_format_stride_for_width()

Use cairo_format_stride_for_width() instead of assuming the pixel size
and manually calculating the row stride. This should make it easier to
support loading multiple image formats in future.
---
 src/cairo-image-surface.c |  1 +
 src/cairo-png.c           | 16 ++++++++++------
 src/cairoint.h            |  1 +
 3 files changed, 12 insertions(+), 6 deletions(-)

diff --git a/src/cairo-image-surface.c b/src/cairo-image-surface.c
index 8247e444e..28e3ce223 100644
--- a/src/cairo-image-surface.c
+++ b/src/cairo-image-surface.c
@@ -440,6 +440,7 @@ cairo_format_stride_for_width (cairo_format_t	format,
 
     return ((bpp*width+7)/8 + STRIDE_ALIGNMENT-1) & ~(STRIDE_ALIGNMENT-1);
 }
+slim_hidden_def (cairo_format_stride_for_width);
 
 /**
  * cairo_image_surface_create_for_data:
diff --git a/src/cairo-png.c b/src/cairo-png.c
index 103061841..de09086ab 100644
--- a/src/cairo-png.c
+++ b/src/cairo-png.c
@@ -399,10 +399,9 @@ read_png (png_rw_ptr	read_func,
     png_info *info;
     png_byte *data = NULL;
     png_byte **row_pointers = NULL;
-    png_uint_32 png_width, png_height, stride;
-    int depth, color_type, interlace;
+    png_uint_32 png_width, png_height;
+    int depth, color_type, interlace, stride;
     unsigned int i;
-    unsigned int pixel_size;
     cairo_status_t status;
 
     /* XXX: Perhaps we'll want some other error handlers? */
@@ -476,8 +475,13 @@ read_png (png_rw_ptr	read_func,
 
     png_read_update_info (png, info);
 
-    pixel_size = 4;
-    data = _cairo_malloc_abc (png_height, png_width, pixel_size);
+    stride = cairo_format_stride_for_width (CAIRO_FORMAT_ARGB32, png_width);
+    if (stride < 0) {
+	surface = _cairo_surface_create_in_error (_cairo_error (CAIRO_STATUS_INVALID_STRIDE));
+	goto BAIL;
+    }
+
+    data = _cairo_malloc_ab (png_height, stride);
     if (data == NULL) {
 	surface = _cairo_surface_create_in_error (_cairo_error (CAIRO_STATUS_NO_MEMORY));
 	goto BAIL;
@@ -490,7 +494,7 @@ read_png (png_rw_ptr	read_func,
     }
 
     for (i = 0; i < png_height; i++)
-        row_pointers[i] = &data[i * png_width * pixel_size];
+        row_pointers[i] = &data[i * stride];
 
     png_read_image (png, row_pointers);
     png_read_end (png, info);
diff --git a/src/cairoint.h b/src/cairoint.h
index 773daf6d4..022033c20 100644
--- a/src/cairoint.h
+++ b/src/cairoint.h
@@ -2244,6 +2244,7 @@ slim_hidden_proto (cairo_image_surface_create);
 slim_hidden_proto (cairo_image_surface_create_for_data);
 slim_hidden_proto (cairo_image_surface_get_height);
 slim_hidden_proto (cairo_image_surface_get_width);
+slim_hidden_proto (cairo_format_stride_for_width);
 slim_hidden_proto (cairo_line_to);
 slim_hidden_proto (cairo_mask);
 slim_hidden_proto (cairo_matrix_init);