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// Copyright (c) 2006-2008 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "base/gfx/point.h"
#include "chrome/browser/tab_contents/tab_contents.h"
#include "chrome/browser/views/tabs/hwnd_photobooth.h"
#include "chrome/common/gfx/chrome_canvas.h"
#include "chrome/views/widget/widget_win.h"
#include "skia/include/SkBitmap.h"
namespace {
static BOOL CALLBACK MonitorEnumProc(HMONITOR monitor, HDC monitor_dc,
RECT* monitor_rect, LPARAM data) {
gfx::Point* point = reinterpret_cast<gfx::Point*>(data);
if (monitor_rect->right > point->x() && monitor_rect->bottom > point->y()) {
point->set_x(monitor_rect->right);
point->set_y(monitor_rect->bottom);
}
return TRUE;
}
gfx::Point GetCaptureWindowPosition() {
// Since the capture window must be visible to be painted, it must be opened
// off screen to avoid flashing. But if it is opened completely off-screen
// (e.g. at 0xFFFFx0xFFFF) then on Windows Vista it will not paint even if it
// _is_ visible. So we need to find the right/bottommost monitor, and
// position it so that 1x1 pixel is on-screen on that monitor which is enough
// to convince Vista to paint it. Don't ask why this is so - this appears to
// be a regression over XP.
gfx::Point point(0, 0);
EnumDisplayMonitors(NULL, NULL, &MonitorEnumProc,
reinterpret_cast<LPARAM>(&point));
return gfx::Point(point.x() - 1, point.y() - 1);
}
}
///////////////////////////////////////////////////////////////////////////////
// HWNDPhotobooth, public:
HWNDPhotobooth::HWNDPhotobooth(HWND initial_hwnd)
: capture_window_(NULL),
current_hwnd_(initial_hwnd) {
DCHECK(IsWindow(current_hwnd_));
CreateCaptureWindow(initial_hwnd);
}
HWNDPhotobooth::~HWNDPhotobooth() {
// Detach the attached HWND. The creator of the photo-booth is responsible
// for destroying it.
ReplaceHWND(NULL);
capture_window_->Close();
}
void HWNDPhotobooth::ReplaceHWND(HWND new_hwnd) {
if (IsWindow(current_hwnd_) &&
GetParent(current_hwnd_) == capture_window_->GetNativeView()) {
// We need to hide the window too, so it doesn't show up in the TaskBar or
// be parented to the desktop.
ShowWindow(current_hwnd_, SW_HIDE);
SetParent(current_hwnd_, NULL);
}
current_hwnd_ = new_hwnd;
if (IsWindow(new_hwnd)) {
// Insert the TabContents into the capture window.
SetParent(current_hwnd_, capture_window_->GetNativeView());
// Show the window (it may not be visible). This is the only safe way of
// doing this. ShowWindow does not work.
SetWindowPos(current_hwnd_, NULL, 0, 0, 0, 0,
SWP_DEFERERASE | SWP_NOACTIVATE | SWP_NOCOPYBITS |
SWP_NOOWNERZORDER | SWP_NOSENDCHANGING | SWP_NOZORDER |
SWP_SHOWWINDOW | SWP_NOSIZE);
}
}
void HWNDPhotobooth::PaintScreenshotIntoCanvas(
ChromeCanvas* canvas,
const gfx::Rect& target_bounds) {
// Our contained window may have been re-parented. Make sure it belongs to
// us until someone calls ReplaceHWND(NULL).
if (IsWindow(current_hwnd_) &&
GetParent(current_hwnd_) != capture_window_->GetNativeView()) {
ReplaceHWND(current_hwnd_);
}
// We compel the contained HWND to paint now, synchronously. We do this to
// populate the device context with valid and current data.
RedrawWindow(current_hwnd_, NULL, NULL, RDW_INVALIDATE | RDW_UPDATENOW);
// Transfer the contents of the layered capture window to the screen-shot
// canvas' DIB.
HDC target_dc = canvas->beginPlatformPaint();
HDC source_dc = GetDC(current_hwnd_);
RECT window_rect = {0};
GetWindowRect(current_hwnd_, &window_rect);
BitBlt(target_dc, target_bounds.x(), target_bounds.y(),
target_bounds.width(), target_bounds.height(), source_dc, 0, 0,
SRCCOPY);
// Windows screws up the alpha channel on all text it draws, and so we need
// to call makeOpaque _after_ the blit to correct for this.
canvas->getTopPlatformDevice().makeOpaque(target_bounds.x(),
target_bounds.y(),
target_bounds.width(),
target_bounds.height());
ReleaseDC(current_hwnd_, source_dc);
canvas->endPlatformPaint();
}
///////////////////////////////////////////////////////////////////////////////
// HWNDPhotobooth, private:
void HWNDPhotobooth::CreateCaptureWindow(HWND initial_hwnd) {
// Snapshotting a HWND is tricky - if the HWND is clipped (e.g. positioned
// partially off-screen) then just blitting from the HWND' DC to the capture
// bitmap would be incorrect, since the capture bitmap would show only the
// visible area of the HWND.
//
// The approach turns out to be to create a second layered window in
// hyperspace the to act as a "photo booth." The window is created with the
// size of the unclipped HWND, and we attach the HWND as a child, refresh the
// HWND' by calling |Paint| on it, and then blitting from the HWND's DC to
// the capture bitmap. This results in the entire unclipped HWND display
// bitmap being captured.
//
// The capture window must be layered so that Windows generates a backing
// store for it, so that blitting from a child window's DC produces data. If
// the window is not layered, because it is off-screen Windows does not
// retain its contents and blitting results in blank data. The capture window
// is a "basic" (1 level of alpha) layered window because that is the mode
// that supports having child windows (variable alpha layered windows do not
// support child HWNDs).
//
// This function sets up the off-screen capture window, and attaches the
// associated HWND to it. Note that the details are important here, see below
// for further comments.
//
CRect contents_rect;
GetClientRect(initial_hwnd, &contents_rect);
gfx::Point window_position = GetCaptureWindowPosition();
gfx::Rect capture_bounds(window_position.x(), window_position.y(),
contents_rect.Width(), contents_rect.Height());
capture_window_ = new views::WidgetWin;
capture_window_->set_window_style(WS_POPUP);
// WS_EX_TOOLWINDOW ensures the capture window doesn't produce a Taskbar
// button.
capture_window_->set_window_ex_style(WS_EX_LAYERED | WS_EX_TOOLWINDOW);
capture_window_->Init(NULL, capture_bounds, false);
// If the capture window isn't visible, blitting from the TabContents'
// HWND's DC to the capture bitmap produces blankness.
capture_window_->Show();
SetLayeredWindowAttributes(
capture_window_->GetNativeView(), RGB(0xFF, 0xFF, 0xFF), 0xFF, LWA_ALPHA);
ReplaceHWND(initial_hwnd);
}
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