Bug 369698: fix dynamic changes to layout.css.dpi pref. r+sr=roc.

gfx/public/nsIDeviceContext.h

@@ -477,6 +477,13 @@ public:
    */
   NS_IMETHOD ClearCachedSystemFonts() = 0;
 
+  /**
+   * Check to see if the DPI has changed
+   * @return whether there was actually a change in the DPI
+   *         (whether AppUnitsPerDevPixel() or AppUnitsPerInch() changed)
+  */
+  virtual PRBool CheckDPIChange() = 0;
+
 protected:
   PRInt32 mAppUnitsPerDevPixel;
   PRInt32 mAppUnitsPerInch;

gfx/src/thebes/nsThebesDeviceContext.cpp

@@ -131,36 +131,38 @@ nsThebesDeviceContext::nsThebesDeviceContext()
 
 nsThebesDeviceContext::~nsThebesDeviceContext()
 {
-    nsresult rv;
-    nsCOMPtr<nsIPref> prefs = do_GetService(NS_PREF_CONTRACTID, &rv);
-    if (NS_SUCCEEDED(rv)) {
-        prefs->UnregisterCallback("layout.css.dpi",
-                                  prefChanged, (void *)this);
-    }
 }
 
 nsresult
-nsThebesDeviceContext::SetDPI(PRInt32 aPrefDPI)
+nsThebesDeviceContext::SetDPI()
 {
     PRInt32 dpi = 96;
 
+    // Set prefVal the value of the preference
+    // "layout.css.dpi"
+    // or -1 if we can't get it.
+    // If it's negative, we pretend it's not set.
+    // If it's 0, it means force use of the operating system's logical
+    // resolution.
+    // If it's positive, we use it as the logical resolution
+    nsresult rv;
+    PRInt32 prefDPI;
+    nsCOMPtr<nsIPref> prefs(do_GetService(NS_PREF_CONTRACTID, &rv));
+    if (NS_SUCCEEDED(rv) && prefs) {
+        rv = prefs->GetIntPref("layout.css.dpi", &prefDPI);
+        if (NS_FAILED(rv)) {
+            prefDPI = -1;
+        }
+    }
+
 #if defined(MOZ_ENABLE_GTK2)
     float screenWidthIn = float(::gdk_screen_width_mm()) / 25.4f;
     PRInt32 OSVal = NSToCoordRound(float(::gdk_screen_width()) / screenWidthIn);
 
-    if (aPrefDPI > 0) {
+    if (prefDPI == 0) // Force the use of the OS dpi
-        // If there's a valid pref value for the logical resolution,
-        // use it.
-        dpi = aPrefDPI;
-    } else if ((aPrefDPI == 0) || (OSVal > 96)) {
-        // Either if the pref is 0 (force use of OS value) or the OS
-        // value is bigger than 96, use the OS value.
         dpi = OSVal;
-    } else {
+    else  // Otherwise, the minimum dpi is 96dpi
-        // if we couldn't get the pref or it's negative, and the OS
+        dpi = PR_MAX(OSVal, 96);
-        // value is under 96ppi, then use 96.
-        dpi = 96;
-    }
 
     if (mPrinter) {
         // cairo printing doesn't really have the
@@ -183,14 +185,16 @@ nsThebesDeviceContext::SetDPI(PRInt32 aPrefDPI)
 
 #elif defined(XP_MACOSX)
 
+    // XXX Need to get the screen DPI instead of defaulting to 96dpi
+
     if (mPrinter) {
         dpi = 72;
     }
 
 #endif
 
-    if (aPrefDPI > 0 && !mPrinter)
+    if (prefDPI > 0 && !mPrinter)
-      dpi = aPrefDPI;
+      dpi = prefDPI;
 
     mAppUnitsPerDevPixel = AppUnitsPerCSSPixel() / PR_MAX(1, (dpi + 48) / 96);
     mAppUnitsPerInch = NSIntPixelsToAppUnits(dpi, mAppUnitsPerDevPixel);
@@ -203,28 +207,7 @@ nsThebesDeviceContext::Init(nsNativeWidget aWidget)
 {
     mWidget = aWidget;
 
-    PRInt32 prefVal = -1;
+    SetDPI();
-
-    // Set prefVal the value of the preference
-    // "layout.css.dpi"
-    // or -1 if we can't get it.
-    // If it's negative, we pretend it's not set.
-    // If it's 0, it means force use of the operating system's logical
-    // resolution.
-    // If it's positive, we use it as the logical resolution
-    nsresult res;
-
-    nsCOMPtr<nsIPref> prefs(do_GetService(NS_PREF_CONTRACTID, &res));
-    if (NS_SUCCEEDED(res) && prefs) {
-        res = prefs->GetIntPref("layout.css.dpi", &prefVal);
-        if (NS_FAILED(res)) {
-            prefVal = -1;
-        }
-        prefs->RegisterCallback("layout.css.dpi", prefChanged,
-                                (void *)this);
-    }
-
-    SetDPI(prefVal);
 
 
 #ifdef MOZ_ENABLE_GTK2
@@ -445,8 +428,8 @@ nsThebesDeviceContext::GetRect(nsRect &aRect)
         // we have a printer device
         aRect.x = 0;
         aRect.y = 0;
-        aRect.width = NSToIntRound(mWidth);
+        aRect.width = mWidth;
-        aRect.height = NSToIntRound(mHeight);
+        aRect.height = mHeight;
     } else
         ComputeFullAreaUsingScreen ( &aRect );
 
@@ -460,8 +443,8 @@ nsThebesDeviceContext::GetClientRect(nsRect &aRect)
         // we have a printer device
         aRect.x = 0;
         aRect.y = 0;
-        aRect.width = NSToIntRound(mWidth);
+        aRect.width = mWidth;
-        aRect.height = NSToIntRound(mHeight);
+        aRect.height = mHeight;
     }
     else
         ComputeClientRectUsingScreen(&aRect);
@@ -586,24 +569,6 @@ nsThebesDeviceContext::EndPage(void)
 
 /** End printing methods **/
 
-int
-nsThebesDeviceContext::prefChanged(const char *aPref, void *aClosure)
-{
-    nsThebesDeviceContext *context = (nsThebesDeviceContext*)aClosure;
-    nsresult rv;
-  
-    if (nsCRT::strcmp(aPref, "layout.css.dpi") == 0) {
-        PRInt32 dpi;
-        nsCOMPtr<nsIPref> prefs(do_GetService(NS_PREF_CONTRACTID, &rv));
-        rv = prefs->GetIntPref(aPref, &dpi);
-        if (NS_SUCCEEDED(rv))
-            context->SetDPI(dpi);
-    }
-
-    return 0;
-}
-
-
 void
 nsThebesDeviceContext::ComputeClientRectUsingScreen(nsRect* outRect)
 {
@@ -716,8 +681,8 @@ nsThebesDeviceContext::CalcPrintingSize()
     }
 
     if (inPoints) {
-        mWidth = float(size.width) * AppUnitsPerInch() / 72;
+        mWidth = NSToCoordRound(float(size.width) * AppUnitsPerInch() / 72);
-        mHeight = float(size.height) * AppUnitsPerInch() / 72;
+        mHeight = NSToCoordRound(float(size.height) * AppUnitsPerInch() / 72);
         printf("%f %f\n", size.width, size.height);
         printf("%d %d\n", (PRInt32)mWidth, (PRInt32)mHeight);
     } else {
@@ -726,3 +691,12 @@ nsThebesDeviceContext::CalcPrintingSize()
     }
 }
 
+PRBool nsThebesDeviceContext::CheckDPIChange() {
+    PRInt32 oldDevPixels = mAppUnitsPerDevPixel;
+    PRInt32 oldInches = mAppUnitsPerInch;
+
+    SetDPI();
+
+    return oldDevPixels != mAppUnitsPerDevPixel ||
+           oldInches != mAppUnitsPerInch;
+}

gfx/src/thebes/nsThebesDeviceContext.h

@@ -112,7 +112,7 @@ public:
 
     static void DebugShowCairoSurface (const char *aName, cairo_surface_t *aSurface);
 
-    static int prefChanged(const char *aPref, void *aClosure);
+    virtual PRBool CheckDPIChange();
 
     nsNativeWidget GetWidget() { return mWidget; }
 #ifdef XP_WIN
@@ -126,7 +126,7 @@ public:
 #endif
 
 protected:
-    nsresult SetDPI(PRInt32 aPrefDPI);
+    nsresult SetDPI();
     void ComputeClientRectUsingScreen(nsRect* outRect);
     void ComputeFullAreaUsingScreen(nsRect* outRect);
     void FindScreen(nsIScreen** outScreen);
@@ -137,8 +137,8 @@ protected:
 private:
     nsCOMPtr<nsIScreenManager> mScreenManager;
 
-    PRInt32 mWidth;
+    nscoord mWidth;
-    PRInt32 mHeight;
+    nscoord mHeight;
     PRBool mPrinter;
 
     nsRefPtrHashtable<nsISupportsHashKey, gfxASurface> mWidgetSurfaceCache;

layout/base/nsPresContext.cpp

@@ -76,6 +76,7 @@
 #include "nsThreadUtils.h"
 #include "nsFrameManager.h"
 #include "nsLayoutUtils.h"
+#include "nsIViewManager.h"
 
 #ifdef IBMBIDI
 #include "nsBidiPresUtils.h"
@@ -273,6 +274,9 @@ nsPresContext::~nsPresContext()
 
   delete mBidiUtils;
 #endif // IBMBIDI
+  nsContentUtils::UnregisterPrefCallback("layout.css.dpi",
+                                         nsPresContext::PrefChangedCallback,
+                                         this);
 
   NS_IF_RELEASE(mDeviceContext);
   NS_IF_RELEASE(mLookAndFeel);
@@ -654,6 +658,21 @@ nsPresContext::ClearStyleDataAndReflow()
 void
 nsPresContext::PreferenceChanged(const char* aPrefName)
 {
+  if (!nsCRT::strcmp(aPrefName, "layout.css.dpi")) {
+    nsRect bounds(mVisibleArea);
+    bounds *= 1.0f / AppUnitsPerDevPixel();
+    if (mDeviceContext->CheckDPIChange() && mShell) {
+      mDeviceContext->FlushFontCache();
+
+      nsIViewManager* vm = GetViewManager();
+      nscoord width = DevPixelsToAppUnits(bounds.width);
+      nscoord height = DevPixelsToAppUnits(bounds.height);
+      vm->SetWindowDimensions(width, height);
+
+      ClearStyleDataAndReflow();
+    }
+    return;
+  }
   // we use a zero-delay timer to coalesce multiple pref updates
   if (!mPrefChangedTimer)
   {
@@ -743,6 +762,9 @@ nsPresContext::Init(nsIDeviceContext* aDeviceContext)
   nsContentUtils::RegisterPrefCallback("bidi.", PrefChangedCallback,
                                        this);
 #endif
+  nsContentUtils::RegisterPrefCallback("layout.css.dpi",
+                                       nsPresContext::PrefChangedCallback,
+                                       this);
 
   rv = mEventManager->Init();
   NS_ENSURE_SUCCESS(rv, rv);