Linux Skia: add an option to build a canvas from a provided memory buffer

Review URL: http://codereview.chromium.org/18678


git-svn-id: svn://svn.chromium.org/chrome/trunk/src@8503 0039d316-1c4b-4281-b951-d872f2087c98

skia/ext/bitmap_platform_device_linux.cc

@@ -41,11 +41,7 @@ class BitmapPlatformDeviceLinux::BitmapPlatformDeviceLinuxData
 // required so that we can call the base class' constructor with the pixel
 // data.
 BitmapPlatformDeviceLinux* BitmapPlatformDeviceLinux::Create(
-    int width, int height, bool is_opaque) {
-  cairo_surface_t* surface =
-      cairo_image_surface_create(CAIRO_FORMAT_ARGB32,
-                                 width, height);
-
+    int width, int height, bool is_opaque, cairo_surface_t* surface) {
   SkBitmap bitmap;
   bitmap.setConfig(SkBitmap::kARGB_8888_Config, width, height,
                    cairo_image_surface_get_stride(surface));
@@ -63,6 +59,24 @@ BitmapPlatformDeviceLinux* BitmapPlatformDeviceLinux::Create(
       (bitmap, new BitmapPlatformDeviceLinuxData(surface));
 }
 
+BitmapPlatformDeviceLinux* BitmapPlatformDeviceLinux::Create(
+    int width, int height, bool is_opaque) {
+  cairo_surface_t* surface =
+      cairo_image_surface_create(CAIRO_FORMAT_ARGB32,
+                                 width, height);
+
+  return Create(width, height, is_opaque, surface);
+}
+
+BitmapPlatformDeviceLinux* BitmapPlatformDeviceLinux::Create(
+    int width, int height, bool is_opaque, uint8_t* data) {
+  cairo_surface_t* surface = cairo_image_surface_create_for_data(
+      data, CAIRO_FORMAT_ARGB32, width, height,
+      cairo_format_stride_for_width(CAIRO_FORMAT_ARGB32, width));
+
+  return Create(width, height, is_opaque, surface);
+}
+
 // The device will own the bitmap, which corresponds to also owning the pixel
 // data. Therefore, we do not transfer ownership to the SkDevice's bitmap.
 BitmapPlatformDeviceLinux::BitmapPlatformDeviceLinux(

skia/ext/bitmap_platform_device_linux.h

@@ -62,6 +62,11 @@ class BitmapPlatformDeviceLinux : public PlatformDeviceLinux {
   /// Static constructor. I don't understand this, it's just a copy of the mac
   static BitmapPlatformDeviceLinux* Create(int width, int height,
                                            bool is_opaque);
+  static BitmapPlatformDeviceLinux* Create(int width, int height,
+                                           bool is_opaque, uint8_t* data);
+  static BitmapPlatformDeviceLinux* Create(int width, int height,
+                                           bool is_opaque,
+                                           cairo_surface_t* surface);
 
   // Create a BitmapPlatformDeviceLinux from an already constructed bitmap;
   // you should probably be using Create(). This may become private later if

skia/ext/platform_canvas_linux.cc

@@ -8,6 +8,8 @@
 #include "skia/ext/bitmap_platform_device_linux.h"
 #include "SkTypes.h"
 
+#include <cairo/cairo.h>
+
 namespace skia {
 
 PlatformCanvasLinux::PlatformCanvasLinux() : SkCanvas() {
@@ -52,4 +54,9 @@ SkDevice* PlatformCanvasLinux::createPlatformDevice(int width,
   return BitmapPlatformDeviceLinux::Create(width, height, is_opaque);
 }
 
+// static
+size_t PlatformCanvasLinux::StrideForWidth(unsigned width) {
+  return cairo_format_stride_for_width(CAIRO_FORMAT_ARGB32, width);
+}
+
 }  // namespace skia

skia/ext/platform_canvas_linux.h

@@ -5,6 +5,8 @@
 #ifndef SKIA_EXT_PLATFORM_CANVAS_LINUX_H_
 #define SKIA_EXT_PLATFORM_CANVAS_LINUX_H_
 
+#include <unistd.h>
+
 #include "skia/ext/platform_device_linux.h"
 
 namespace skia {
@@ -21,6 +23,9 @@ class PlatformCanvasLinux : public SkCanvas {
   // If you use the version with no arguments, you MUST call initialize()
   PlatformCanvasLinux();
   PlatformCanvasLinux(int width, int height, bool is_opaque);
+  // Construct a canvas from the given memory region. The memory is not cleared
+  // first. @data must be, at least, @height * StrideForWidth(@width) bytes.
+  PlatformCanvasLinux(int width, int height, bool is_opaque, uint8_t* data);
   virtual ~PlatformCanvasLinux();
 
   // For two-part init, call if you use the no-argument constructor above
@@ -31,6 +36,11 @@ class PlatformCanvasLinux : public SkCanvas {
   // a Linux version is added for compatibility.
   PlatformDeviceLinux& getTopPlatformDevice() const;
 
+  // Return the stride (length of a line in bytes) for the given width. Because
+  // we use 32-bits per pixel, this will be roughly 4*width. However, for
+  // alignment reasons we may wish to increase that.
+  static size_t StrideForWidth(unsigned width);
+
  protected:
   // Creates a device store for use by the canvas. We override this so that
   // the device is always our own so we know that we can use GDI operations