Bug 1577258 - Streamline the shrink-wrapping resize reflow code. r=botond

Now that this code path is on its own, we can write more straight-forward code.



Depends on D43799

Differential Revision: https://phabricator.services.mozilla.com/D43800

--HG--
extra : moz-landing-system : lando

layout/base/PresShell.cpp

@@ -1913,8 +1913,19 @@ nsresult PresShell::ResizeReflowIgnoreOverride(nscoord aWidth, nscoord aHeight,
     return NS_OK;
   }
 
-  nsIFrame* rootFrame = mFrameConstructor->GetRootFrame();
-  if (!rootFrame) {
+  MOZ_ASSERT(!mPresContext->SuppressingResizeReflow(),
+             "Can't suppress resize reflow and shrink-wrap at the same time");
+
+  // Make sure that style is flushed before setting the pres context
+  // VisibleArea.
+  //
+  // Otherwise we may end up with bogus viewport units resolved against the
+  // unconstrained bsize, or restyling the whole document resolving viewport
+  // units against targetWidth, which may end up doing wasteful work.
+  mDocument->FlushPendingNotifications(FlushType::Frames);
+
+  nsIFrame* rootFrame = GetRootFrame();
+  if (mIsDestroying || !rootFrame) {
     // If we don't have a root frame yet, that means we haven't had our initial
     // reflow... If that's the case, and aWidth or aHeight is unconstrained,
     // ignore them altogether.
@@ -1931,68 +1942,25 @@ nsresult PresShell::ResizeReflowIgnoreOverride(nscoord aWidth, nscoord aHeight,
   }
 
   WritingMode wm = rootFrame->GetWritingMode();
-  const bool shrinkToFit = !!(aOptions & ResizeReflowOptions::BSizeLimit);
-  MOZ_ASSERT(shrinkToFit ||
-                 (wm.IsVertical() ? aWidth : aHeight) != NS_UNCONSTRAINEDSIZE,
-             "unconstrained bsize only usable with eBSizeLimit");
   MOZ_ASSERT((wm.IsVertical() ? aHeight : aWidth) != NS_UNCONSTRAINEDSIZE,
              "unconstrained isize not allowed");
-  bool isBSizeChanging =
-      wm.IsVertical() ? aOldWidth != aWidth : aOldHeight != aHeight;
+
   nscoord targetWidth = aWidth;
   nscoord targetHeight = aHeight;
-
-  if (shrinkToFit) {
   if (wm.IsVertical()) {
     targetWidth = NS_UNCONSTRAINEDSIZE;
   } else {
     targetHeight = NS_UNCONSTRAINEDSIZE;
   }
-    isBSizeChanging = true;
-  }
 
-  const bool suppressingResizeReflow =
-      GetPresContext()->SuppressingResizeReflow();
-
-  RefPtr<nsViewManager> viewManager = mViewManager;
-  if (!suppressingResizeReflow && shrinkToFit) {
-    // Make sure that style is flushed before setting the pres context
-    // VisibleArea if we're shrinking to fit.
-    //
-    // Otherwise we may end up with bogus viewport units resolved against the
-    // unconstrained bsize, or restyling the whole document resolving viewport
-    // units against targetWidth, which may end up doing wasteful work.
-    mDocument->FlushPendingNotifications(FlushType::Frames);
-  }
-
-  if (!mIsDestroying) {
   mPresContext->SetVisibleArea(nsRect(0, 0, targetWidth, targetHeight));
-  }
-
-  if (!mIsDestroying && !suppressingResizeReflow) {
-    if (!shrinkToFit) {
-      // Flush styles _now_ (with the correct visible area) if not computing the
-      // shrink-to-fit size.
-      //
-      // We've asserted above that sizes are not unconstrained, so this is going
-      // to be the final size, which means that we'll get the (correct) final
-      // styles now, and avoid a further potentially-wasteful full recascade on
-      // the next flush.
-      mDocument->FlushPendingNotifications(FlushType::Frames);
-    }
-
-    rootFrame = mFrameConstructor->GetRootFrame();
-    if (!mIsDestroying && rootFrame) {
   // XXX Do a full invalidate at the beginning so that invalidates along
   // the way don't have region accumulation issues?
 
-      if (isBSizeChanging) {
-        // For BSize changes driven by style, RestyleManager handles this.
   // For height:auto BSizes (i.e. layout-controlled), descendant
   // intrinsic sizes can't depend on them. So the only other case is
   // viewport-controlled BSizes which we handle here.
   nsLayoutUtils::MarkIntrinsicISizesDirtyIfDependentOnBSize(rootFrame);
-      }
 
   {
     nsAutoCauseReflowNotifier crNotifier(this);
@@ -2000,12 +1968,11 @@ nsresult PresShell::ResizeReflowIgnoreOverride(nscoord aWidth, nscoord aHeight,
 
     // Kick off a top-down reflow
     AUTO_LAYOUT_PHASE_ENTRY_POINT(GetPresContext(), Reflow);
-        nsViewManager::AutoDisableRefresh refreshBlocker(viewManager);
+    nsViewManager::AutoDisableRefresh refreshBlocker(mViewManager);
 
     mDirtyRoots.Remove(rootFrame);
     DoReflow(rootFrame, true, nullptr);
 
-        if (shrinkToFit) {
     const bool reflowAgain =
         wm.IsVertical() ? mPresContext->GetVisibleArea().width > aWidth
                         : mPresContext->GetVisibleArea().height > aHeight;
@@ -2015,39 +1982,17 @@ nsresult PresShell::ResizeReflowIgnoreOverride(nscoord aWidth, nscoord aHeight,
       DoReflow(rootFrame, true, nullptr);
     }
   }
-      }
-
-      // the first DoReflow above should've set our bsize if it was
-      // NS_UNCONSTRAINEDSIZE, and the isize shouldn't be NS_UNCONSTRAINEDSIZE
-      // anyway
-      NS_ASSERTION(mPresContext->GetVisibleArea().width != NS_UNCONSTRAINEDSIZE,
-                   "width should not be NS_UNCONSTRAINEDSIZE after reflow");
-      NS_ASSERTION(
-          mPresContext->GetVisibleArea().height != NS_UNCONSTRAINEDSIZE,
-          "height should not be NS_UNCONSTRAINEDSIZE after reflow");
 
   DidDoReflow(true);
-    }
-  }
 
-  rootFrame = mFrameConstructor->GetRootFrame();
-  if (rootFrame) {
-    wm = rootFrame->GetWritingMode();
-    // reflow did not happen; if the reflow happened, our bsize should not be
-    // NS_UNCONSTRAINEDSIZE because DoReflow will fix it up to the same values
-    // as below
-    if (wm.IsVertical()) {
-      if (mPresContext->GetVisibleArea().width == NS_UNCONSTRAINEDSIZE) {
-        mPresContext->SetVisibleArea(
-            nsRect(0, 0, rootFrame->GetRect().width, aHeight));
-      }
-    } else {
-      if (mPresContext->GetVisibleArea().height == NS_UNCONSTRAINEDSIZE) {
-        mPresContext->SetVisibleArea(
-            nsRect(0, 0, aWidth, rootFrame->GetRect().height));
-      }
-    }
-  }
+  // the reflow above should've set our bsize if it was NS_UNCONSTRAINEDSIZE,
+  // and the isize shouldn't be NS_UNCONSTRAINEDSIZE anyway.
+  MOZ_DIAGNOSTIC_ASSERT(
+      mPresContext->GetVisibleArea().width != NS_UNCONSTRAINEDSIZE,
+      "width should not be NS_UNCONSTRAINEDSIZE after reflow");
+  MOZ_DIAGNOSTIC_ASSERT(
+      mPresContext->GetVisibleArea().height != NS_UNCONSTRAINEDSIZE,
+      "height should not be NS_UNCONSTRAINEDSIZE after reflow");
 
   postResizeEventIfNeeded();
   return NS_OK;  // XXX this needs to be real. MMP