Bug 616664 - nsIScreen interface for keeping the screen on. r=blassey sr=roc a=blocking-fennec

widget/public/nsIScreen.idl

@@ -53,3 +53,34 @@ interface nsIScreen : nsISupports
 %{ C++
 
 %}
+
+[scriptable, uuid(f7c93d20-c4e4-4628-b343-cb5530b04f15)]
+interface nsIScreen_MOZILLA_2_0_BRANCH : nsISupports {
+  /**
+   * Levels of brightness for the screen, from off to full brightness.
+   */
+  const unsigned long BRIGHTNESS_DIM = 0;
+  const unsigned long BRIGHTNESS_FULL = 1;
+
+  /* The number of different brightness levels */
+  const unsigned long BRIGHTNESS_LEVELS = 2;
+
+  /**
+   * Locks the minimum brightness of the screen, forcing it to be at
+   * least as bright as a certain brightness level. Each call to this
+   * function must eventually be followed by a corresponding call to
+   * unlockMinimumBrightness, with the same brightness level.
+   *
+   * @param brightness A brightness level, one of the above constants.
+   */
+  void lockMinimumBrightness(in unsigned long brightness);
+
+  /**
+   * Releases a lock on the screen brightness. This must be called
+   * (eventually) after a corresponding call to lockMinimumBrightness.
+   *
+   * @param brightness A brightness level, one of the above constants.
+   */
+  void unlockMinimumBrightness(in unsigned long brightness);
+};
+

widget/src/shared/WidgetUtils.cpp

@@ -80,5 +80,54 @@ WidgetUtils::DOMWindowToWidget(nsIDOMWindow *aDOMWindow)
   return widget.forget();
 }
 
+// class BrightnessLockingWidget
+
+BrightnessLockingWidget::BrightnessLockingWidget()
+{
+  for (PRUint32 i = 0; i < nsIScreen_MOZILLA_2_0_BRANCH::BRIGHTNESS_LEVELS; i++)
+    mBrightnessLocks[i] = 0;
+}
+
+NS_IMETHODIMP
+BrightnessLockingWidget::LockMinimumBrightness(PRUint32 aBrightness)
+{
+  NS_ABORT_IF_FALSE(
+    aBrightness < nsIScreen_MOZILLA_2_0_BRANCH::BRIGHTNESS_LEVELS,
+    "Invalid brightness level to lock");
+  mBrightnessLocks[aBrightness]++;
+  NS_ABORT_IF_FALSE(mBrightnessLocks[aBrightness] > 0,
+    "Overflow after locking brightness level");
+
+  CheckMinimumBrightness();
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+BrightnessLockingWidget::UnlockMinimumBrightness(PRUint32 aBrightness)
+{
+  NS_ABORT_IF_FALSE(
+    aBrightness < nsIScreen_MOZILLA_2_0_BRANCH::BRIGHTNESS_LEVELS,
+    "Invalid brightness level to lock");
+  NS_ABORT_IF_FALSE(mBrightnessLocks[aBrightness] > 0,
+    "Unlocking a brightness level with no corresponding lock");
+  mBrightnessLocks[aBrightness]--;
+
+  CheckMinimumBrightness();
+
+  return NS_OK;
+}
+
+void
+BrightnessLockingWidget::CheckMinimumBrightness()
+{
+  PRUint32 brightness = nsIScreen_MOZILLA_2_0_BRANCH::BRIGHTNESS_LEVELS;
+  for (PRUint32 i = 0; i < nsIScreen_MOZILLA_2_0_BRANCH::BRIGHTNESS_LEVELS; i++)
+    if (mBrightnessLocks[i] > 0)
+      brightness = i;
+
+  ApplyMinimumBrightness(brightness);
+}
+
 } // namespace widget
 } // namespace mozilla

widget/src/shared/WidgetUtils.h

@@ -45,6 +45,7 @@
 #include "nsIWidget.h"
 #include "nsPIDOMWindow.h"
 #include "nsIDOMWindow.h"
+#include "nsIScreen.h"
 
 namespace mozilla {
 namespace widget {
@@ -60,6 +61,46 @@ public:
   static already_AddRefed<nsIWidget> DOMWindowToWidget(nsIDOMWindow *aDOMWindow);
 };
 
+/**
+ * Simple management of screen brightness locks. This abstract base class
+ * allows all widget implementations to share brightness locking code.
+ */
+class BrightnessLockingWidget : public nsIScreen_MOZILLA_2_0_BRANCH
+{
+public:
+  BrightnessLockingWidget();
+
+  NS_IMETHOD LockMinimumBrightness(PRUint32 aBrightness);
+  NS_IMETHOD UnlockMinimumBrightness(PRUint32 aBrightness);
+
+protected:
+  /**
+   * Manually set the current level of brightness locking. This is called after
+   * we determine, based on the current active locks, what the strongest
+   * lock is. You should normally not call this function - it will be
+   * called automatically by this class.
+   *
+   * Each widget implementation should implement this in a way that
+   * makes sense there. This is normally the only function that
+   * contains widget-specific code.
+   *
+   * @param aBrightness The current brightness level to set. If this is
+   *                    nsIScreen_MOZILLA_2_0_BRANCH::BRIGHTNESS_LEVELS
+   *                    (an impossible value for a brightness level to be),
+   *                    then that signifies that there is no current
+   *                    minimum brightness level, and the screen can shut off.
+   */
+  virtual void ApplyMinimumBrightness(PRUint32 aBrightness) = 0;
+
+  /**
+   * Checks what the minimum brightness value is, and calls
+   * ApplyMinimumBrightness.
+   */
+  void CheckMinimumBrightness();
+
+  PRUint32 mBrightnessLocks[nsIScreen_MOZILLA_2_0_BRANCH::BRIGHTNESS_LEVELS];
+};
+
 } // namespace widget
 } // namespace mozilla