gfx/thebes/PrintTargetRecording.cpp

   1 /* -*- Mode: C++; tab-width: 20; indent-tabs-mode: nil; c-basic-offset: 2 -*-
   2  * This Source Code Form is subject to the terms of the Mozilla Public
   3  * License, v. 2.0. If a copy of the MPL was not distributed with this
   4  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   5
   6 #include "PrintTargetRecording.h"
   7
   8 #include "cairo.h"
   9 #include "mozilla/gfx/2D.h"
  10 #include "mozilla/gfx/Logging.h"
  11
  12 namespace mozilla {
  13 namespace gfx {
  14
  15 PrintTargetRecording::PrintTargetRecording(cairo_surface_t* aCairoSurface,
  16                                            const IntSize& aSize)
  17     : PrintTarget(aCairoSurface, aSize) {}
  18
  19 /* static */
  20 already_AddRefed<PrintTargetRecording> PrintTargetRecording::CreateOrNull(
  21     const IntSize& aSize) {
  22   if (!Factory::CheckSurfaceSize(aSize)) {
  23     return nullptr;
  24   }
  25
  26   // Perhaps surprisingly, this surface is never actually drawn to.  This class
  27   // creates a DrawTargetRecording using CreateRecordingDrawTarget, and
  28   // that needs another DrawTarget to be passed to it.  You might expect the
  29   // type of the DrawTarget that is passed to matter because it would seem
  30   // logical to encoded its type in the recording, and on replaying the
  31   // recording a DrawTarget of the same type would be created.  However, the
  32   // passed DrawTarget's type doesn't seem to be encoded any more accurately
  33   // than just "BackendType::CAIRO".  Even if it were, the code that replays the
  34   // recording is PrintTranslator::TranslateRecording which (indirectly) calls
  35   // MakePrintTarget on the type of nsIDeviceContextSpecProxy that is created
  36   // for the platform that we're running on, and the type of DrawTarget that
  37   // that returns is hardcoded.
  38   //
  39   // The only reason that we use cairo_recording_surface_create here is:
  40   //
  41   //   * It's pretty much the only cairo_*_surface_create methods that's both
  42   //     available on all platforms and doesn't require allocating a
  43   //     potentially large surface.
  44   //
  45   //   * Since we need a DrawTarget to pass to CreateRecordingDrawTarget we
  46   //     might as well leverage our base class's machinery to create a
  47   //     DrawTarget (it's as good a way as any other that will work), and to do
  48   //     that we need a cairo_surface_t.
  49   //
  50   // So the fact that this is a "recording" PrintTarget and the function that
  51   // we call here is cairo_recording_surface_create is simply a coincidence. We
  52   // could use any cairo_*_surface_create method and this class would still
  53   // work.
  54   //
  55   cairo_surface_t* surface =
  56       cairo_recording_surface_create(CAIRO_CONTENT_COLOR_ALPHA, nullptr);
  57
  58   if (cairo_surface_status(surface)) {
  59     return nullptr;
  60   }
  61
  62   // The new object takes ownership of our surface reference.
  63   RefPtr<PrintTargetRecording> target =
  64       new PrintTargetRecording(surface, aSize);
  65
  66   return target.forget();
  67 }
  68
  69 already_AddRefed<DrawTarget> PrintTargetRecording::MakeDrawTarget(
  70     const IntSize& aSize, DrawEventRecorder* aRecorder) {
  71   MOZ_ASSERT(aRecorder, "A DrawEventRecorder is required");
  72
  73   if (!aRecorder) {
  74     return nullptr;
  75   }
  76
  77   RefPtr<DrawTarget> dt = PrintTarget::MakeDrawTarget(aSize, nullptr);
  78   if (dt) {
  79     dt = CreateRecordingDrawTarget(aRecorder, dt);
  80     if (!dt || !dt->IsValid()) {
  81       return nullptr;
  82     }
  83   }
  84
  85   return dt.forget();
  86 }
  87
  88 already_AddRefed<DrawTarget> PrintTargetRecording::CreateRecordingDrawTarget(
  89     DrawEventRecorder* aRecorder, DrawTarget* aDrawTarget) {
  90   MOZ_ASSERT(aRecorder);
  91   MOZ_ASSERT(aDrawTarget);
  92
  93   RefPtr<DrawTarget> dt;
  94
  95   if (aRecorder) {
  96     // It doesn't really matter what we pass as the DrawTarget here.
  97     dt = gfx::Factory::CreateRecordingDrawTarget(aRecorder, aDrawTarget,
  98                                                  aDrawTarget->GetRect());
  99   }
 100
 101   if (!dt || !dt->IsValid()) {
 102     gfxCriticalNote
 103         << "Failed to create a recording DrawTarget for PrintTarget";
 104     return nullptr;
 105   }
 106
 107   return dt.forget();
 108 }
 109
 110 }  // namespace gfx
 111 }  // namespace mozilla