widget/DimensionRequest.h

   1 /* This Source Code Form is subject to the terms of the Mozilla Public
   2  * License, v. 2.0. If a copy of the MPL was not distributed with this
   3  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   4
   5 #ifndef mozilla_DimensionRequest_h
   6 #define mozilla_DimensionRequest_h
   7
   8 #include "Units.h"
   9 #include "mozilla/Maybe.h"
  10
  11 class nsIBaseWindow;
  12 class nsIDocShellTreeOwner;
  13
  14 namespace mozilla {
  15
  16 enum class DimensionKind { Inner, Outer };
  17
  18 /**
  19  * DimensionRequest allows to request the change of some dimensions without
  20  * having to specify the unchanged dimensions. This is specifically necessary
  21  * when a change is initiated from a child process, which might not have an
  22  * up-to-date view of its latest dimensions. Having to specify the missing
  23  * dimensions with an outdated view can revert a previous change.
  24  *
  25  * The following series of changes `window.screenX = 10; window.screenY = 10;`
  26  * essentially translates into two moveTo() calls. For the second call we want
  27  * to account for changes made by the first call. From a child process we would
  28  * end up crafting the second call without knowing the results of the first
  29  * call. In the parent process we have access to results of the first call
  30  * before crafting the second one. Although on Linux even the parent process
  31  * doesn't have immediate access to the results of the last change.
  32  *
  33  * Note: The concept of an inner position is not present on
  34  * nsIDocShellTreeOwner and nsIBaseWindow. A request specifying an inner
  35  * position will return an NS_ERROR_NOT_IMPLEMENTED.
  36  */
  37 struct DimensionRequest {
  38   DimensionKind mDimensionKind;
  39   Maybe<LayoutDeviceIntCoord> mX;
  40   Maybe<LayoutDeviceIntCoord> mY;
  41   Maybe<LayoutDeviceIntCoord> mWidth;
  42   Maybe<LayoutDeviceIntCoord> mHeight;
  43
  44   /**
  45    * Fills the missing dimensions with values obtained from `aSource`. Whether
  46    * inner dimensions are supported depends on the implementation of
  47    * `nsIBaseWindow::GetDimensions` for `aSource`.
  48    *
  49    * @param aSource  The source for the missing dimensions.
  50    */
  51   nsresult SupplementFrom(nsIBaseWindow* aSource);
  52
  53   /**
  54    * Changes the outer size and or position of `aTarget`. Only outer dimensions
  55    * are supported.
  56    *
  57    * @param aTarget  The target whose size or position we want to change.
  58    */
  59   nsresult ApplyOuterTo(nsIBaseWindow* aTarget);
  60
  61   /**
  62    * Changes the inner size of `aTarget`. Only inner dimensions are supported.
  63    *
  64    * @param aTarget  The target whose size we want to change.
  65    */
  66   nsresult ApplyInnerTo(nsIDocShellTreeOwner* aTarget, bool aAsRootShell);
  67 };
  68
  69 }  // namespace mozilla
  70
  71 #endif  // mozilla_DimensionRequest_h