Refine autozoom scaling constants and logic

Source/web/WebViewImpl.cpp

 /*
  * Copyright (C) 2011, 2012 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 177 matching lines @@
 
 static const double multipleTargetsZoomAnimationDurationInSeconds = 0.25;
 static const double findInPageAnimationDurationInSeconds = 0;
 
 // Constants for viewport anchoring on resize.
 static const float viewportAnchorXCoord = 0.5f;
 static const float viewportAnchorYCoord = 0;
 
 // Constants for zooming in on a focused text field.
 static const double scrollAndScaleAnimationDurationInSeconds = 0.2;
-static const int minReadableCaretHeight = 18;
-static const float minScaleChangeToTriggerZoom = 1.05f;
+static const int minReadableCaretHeight = 16;
+static const int minReadableCaretHeightForTextArea = 13;
+static const float minScaleChangeToTriggerZoom = 1.5f;
 static const float leftBoxRatio = 0.3f;
 static const int caretPadding = 10;
 
 namespace blink {
 
 // Change the text zoom level by kTextSizeMultiplierRatio each time the user
 // zooms text in or out (ie., change by 20%).  The min and max values limit
 // text zoom to half and 3x the original text size.  These three values match
 // those in Apple's port in WebKit/WebKit/WebView/WebView.mm
 const double WebView::textSizeMultiplierRatio = 1.2;
@@ skipping 2640 matching lines @@
     focusedNode->document().updateLayoutIgnorePendingStylesheets();
 
     // 'caret' is rect encompassing the blinking cursor.
     IntRect textboxRect = focusedNode->document().view()->contentsToWindow(pixelSnappedIntRect(focusedNode->Node::boundingBox()));
     WebRect caret, unusedEnd;
     selectionBounds(caret, unusedEnd);
     IntRect unscaledCaret = caret;
     unscaledCaret.scale(1 / pageScaleFactor());
     caret = unscaledCaret;
 
-    // Pick a scale which is reasonably readable. This is the scale at which
-    // the caret height will become minReadableCaretHeight (adjusted for dpi
-    // and font scale factor).
-    newScale = clampPageScaleFactorToLimits(legibleScale() * minReadableCaretHeight / caret.height);
-    newScale = std::max(newScale, pageScaleFactor());
+    if (shouldDisableDesktopWorkarounds()) {
+        newScale = pageScaleFactor();
+    } else {
+        // Pick a scale which is reasonably readable. This is the scale at which
+        // the caret height will become minReadableCaretHeightForNode (adjusted
+        // for dpi and font scale factor).
+        const int minReadableCaretHeightForNode = textboxRect.height() >= 2 * caret.height ? minReadableCaretHeightForTextArea : minReadableCaretHeight;
+        newScale = clampPageScaleFactorToLimits(legibleScale() * minReadableCaretHeightForNode / caret.height);
+        newScale = std::max(newScale, pageScaleFactor());
+    }
     const float deltaScale = newScale / pageScaleFactor();
 
+    needAnimation = false;
+    // If we are at less than the target zoom level, zoom in.
+    if (deltaScale > minScaleChangeToTriggerZoom)
+        needAnimation = true;
+    else
+        newScale = pageScaleFactor();
+
     // Convert the rects to absolute space in the new scale.
     IntRect textboxRectInDocumentCoordinates = textboxRect;
     textboxRectInDocumentCoordinates.move(mainFrame()->scrollOffset());
     IntRect caretInDocumentCoordinates = caret;
     caretInDocumentCoordinates.move(mainFrame()->scrollOffset());
 
     int viewWidth = m_size.width / newScale;
     int viewHeight = m_size.height / newScale;
 
+    // If the caret is offscreen, then animate.
+    IntRect sizeRect(0, 0, viewWidth, viewHeight);
+    sizeRect.scale(newScale / pageScaleFactor());
+    if (!sizeRect.contains(caret))
+        needAnimation = true;
+
+    // If the box is partially offscreen and it's possible to bring it fully
+    // onscreen, then animate.
+    if (sizeRect.contains(textboxRectInDocumentCoordinates.width(), textboxRectInDocumentCoordinates.height()) && !sizeRect.contains(textboxRect))
+        needAnimation = true;
+
+    if (!needAnimation)
+        return;
+
     if (textboxRectInDocumentCoordinates.width() <= viewWidth) {
         // Field is narrower than screen. Try to leave padding on left so field's
         // label is visible, but it's more important to ensure entire field is
         // onscreen.
         int idealLeftPadding = viewWidth * leftBoxRatio;
         int maxLeftPaddingKeepingBoxOnscreen = viewWidth - textboxRectInDocumentCoordinates.width();
         newScroll.setX(textboxRectInDocumentCoordinates.x() - std::min<int>(idealLeftPadding, maxLeftPaddingKeepingBoxOnscreen));
     } else {
         // Field is wider than screen. Try to left-align field, unless caret would
         // be offscreen, in which case right-align the caret.
         newScroll.setX(std::max<int>(textboxRectInDocumentCoordinates.x(), caretInDocumentCoordinates.x() + caretInDocumentCoordinates.width() + caretPadding - viewWidth));
     }
     if (textboxRectInDocumentCoordinates.height() <= viewHeight) {
         // Field is shorter than screen. Vertically center it.
         newScroll.setY(textboxRectInDocumentCoordinates.y() - (viewHeight - textboxRectInDocumentCoordinates.height()) / 2);
     } else {
         // Field is taller than screen. Try to top align field, unless caret would
         // be offscreen, in which case bottom-align the caret.
         newScroll.setY(std::max<int>(textboxRectInDocumentCoordinates.y(), caretInDocumentCoordinates.y() + caretInDocumentCoordinates.height() + caretPadding - viewHeight));
     }
-
-    needAnimation = false;
-    // If we are at less than the target zoom level, zoom in.
-    if (deltaScale > minScaleChangeToTriggerZoom)
-        needAnimation = true;
-    // If the caret is offscreen, then animate.
-    IntRect sizeRect(0, 0, viewWidth, viewHeight);
-    sizeRect.scale(newScale / pageScaleFactor());
-    if (!sizeRect.contains(caret))
-        needAnimation = true;
-    // If the box is partially offscreen and it's possible to bring it fully
-    // onscreen, then animate.
-    if (sizeRect.contains(textboxRectInDocumentCoordinates.width(), textboxRectInDocumentCoordinates.height()) && !sizeRect.contains(textboxRect))
-        needAnimation = true;
 }
 
 void WebViewImpl::advanceFocus(bool reverse)
 {
     page()->focusController().advanceFocus(reverse ? FocusTypeBackward : FocusTypeForward);
 }
 
 double WebViewImpl::zoomLevel()
 {
     return m_zoomLevel;
@@ skipping 1605 matching lines @@
     return mainFrameImpl()->frameView()->layoutSize().width() == m_size.width
         || (constraints.minimumScale == constraints.maximumScale && constraints.minimumScale != -1);
 }
 
 void WebViewImpl::forceNextWebGLContextCreationToFail()
 {
     WebGLRenderingContext::forceNextWebGLContextCreationToFail();
 }
 
 } // namespace blink