Changeset 232435 in webkit

Timestamp:

Jun 1, 2018 11:54:12 PM (6 years ago)

Author:

Wenson Hsieh

Message:

[Extra zoom mode] The user should always be able to double tap to zoom to a scale of at least 1
​https://bugs.webkit.org/show_bug.cgi?id=186209
<rdar://problem/40529255>

Reviewed by Tim Horton.

Source/WebKit:

Tweaks the way double-tap-to-zoom scales are determined in extra zoom mode. Rather than zooming to make the 50th
and 90th percentiles of text in the document legible, only consider the 90th percentile of text size when
determining zoom scale, and fix the other potential zoom scale at 1; additionally, if the zoom scales are close
(within 0.3 of each other), snap the lower zoom scale to the higher value.

This results in the following changes in behavior:

• Enables double tap to zoom in cases where all the text in the page is already legible.
• On pages with mobile viewports, usually allows the user to toggle between initial scale and a scale of 1.
• If a significant portion of text is unusually small, the zoomed-in scale may exceed 1.

Test: fast/events/extrazoom/double-tap-to-zoom-with-large-text.html

• WebProcess/WebPage/ViewGestureGeometryCollector.cpp:

(WebKit::ViewGestureGeometryCollector::collectGeometryForSmartMagnificationGesture):
(WebKit::ViewGestureGeometryCollector::computeTextLegibilityScales):

LayoutTests:

Add a test to verify that double tapping zooms in on a page where all the text is large enough to be legible at
initial scale.

• fast/events/extrazoom/double-tap-to-zoom-with-large-text-expected.txt: Added.
• fast/events/extrazoom/double-tap-to-zoom-with-large-text.html: Added.

Location:

trunk

Files:

• LayoutTests/ChangeLog (modified) (1 diff)
• LayoutTests/fast/events/extrazoom/double-tap-to-zoom-with-large-text-expected.txt (added)
• LayoutTests/fast/events/extrazoom/double-tap-to-zoom-with-large-text.html (added)
• Source/WebKit/ChangeLog (modified) (1 diff)
• Source/WebKit/WebProcess/WebPage/ViewGestureGeometryCollector.cpp (modified) (4 diffs)

trunk/LayoutTests/ChangeLog

@@ +1 @@
+2018-06-01  Wenson Hsieh  <wenson_hsieh@apple.com>
+
+        [Extra zoom mode] The user should always be able to double tap to zoom to a scale of at least 1
+        https://bugs.webkit.org/show_bug.cgi?id=186209
+        <rdar://problem/40529255>
+
+        Reviewed by Tim Horton.
+
+        Add a test to verify that double tapping zooms in on a page where all the text is large enough to be legible at
+        initial scale.
+
+        * fast/events/extrazoom/double-tap-to-zoom-with-large-text-expected.txt: Added.
+        * fast/events/extrazoom/double-tap-to-zoom-with-large-text.html: Added.
+
 2018-06-01  Ryosuke Niwa  <rniwa@webkit.org>
 

trunk/Source/WebKit/ChangeLog

@@ +1 @@
+2018-06-01  Wenson Hsieh  <wenson_hsieh@apple.com>
+
+        [Extra zoom mode] The user should always be able to double tap to zoom to a scale of at least 1
+        https://bugs.webkit.org/show_bug.cgi?id=186209
+        <rdar://problem/40529255>
+
+        Reviewed by Tim Horton.
+
+        Tweaks the way double-tap-to-zoom scales are determined in extra zoom mode. Rather than zooming to make the 50th
+        and 90th percentiles of text in the document legible, only consider the 90th percentile of text size when
+        determining zoom scale, and fix the other potential zoom scale at 1; additionally, if the zoom scales are close
+        (within 0.3 of each other), snap the lower zoom scale to the higher value.
+
+        This results in the following changes in behavior:
+        -   Enables double tap to zoom in cases where all the text in the page is already legible.
+        -   On pages with mobile viewports, usually allows the user to toggle between initial scale and a scale of 1.
+        -   If a significant portion of text is unusually small, the zoomed-in scale may exceed 1.
+
+        Test: fast/events/extrazoom/double-tap-to-zoom-with-large-text.html
+
+        * WebProcess/WebPage/ViewGestureGeometryCollector.cpp:
+        (WebKit::ViewGestureGeometryCollector::collectGeometryForSmartMagnificationGesture):
+        (WebKit::ViewGestureGeometryCollector::computeTextLegibilityScales):
+
 2018-06-01  Jeremy Jones  <jeremyj@apple.com>
 

trunk/Source/WebKit/WebProcess/WebPage/ViewGestureGeometryCollector.cpp

@@ -55 +55 @@
 namespace WebKit {
 
+#if PLATFORM(IOS)
+static const double minimumScaleDifferenceForZooming = 0.3;
+#endif
+
 ViewGestureGeometryCollector::ViewGestureGeometryCollector(WebPage& webPage)
     : m_webPage(webPage)
@@ -91 +95 @@
 #if PLATFORM(IOS)
     if (m_webPage.platformPrefersTextLegibilityBasedZoomScaling()) {
-        static const double minimumScaleDifferenceForZooming = 0.05;
-
         auto textLegibilityScales = computeTextLegibilityScales(viewportMinimumScale, viewportMaximumScale);
         if (!textLegibilityScales) {
@@ -144 +146 @@
 
     static const double targetLegibilityFontSize = 12;
-    static const double firstTextLegibilityScaleRatio = 0.5;
-    static const double secondTextLegibilityScaleRatio = 0.1;
-    static const double minimumDifferenceBetweenTextLegibilityScales = 0.2;
-    static const double fallbackTextLegibilityScale = 1;
+    static const double textLegibilityScaleRatio = 0.1;
+    static const double defaultTextLegibilityZoomScale = 1;
 
     computeMinimumAndMaximumViewportScales(viewportMinimumScale, viewportMaximumScale);
@@ -194 +194 @@
     });
 
-    double firstTextLegibilityScale = 0;
-    double secondTextLegibilityScale = 0;
+    double defaultScale = clampTo<double>(defaultTextLegibilityZoomScale, viewportMinimumScale, viewportMaximumScale);
+    double textLegibilityScale = defaultScale;
     double currentSampledTextLength = 0;
     for (auto& fontSizeAndCount : sortedFontSizesAndCounts) {
         currentSampledTextLength += fontSizeAndCount.count;
         double ratioOfTextUnderCurrentFontSize = currentSampledTextLength / totalSampledTextLength;
-        LOG(ViewGestures, "About %.2f%% of text is smaller than font size %tu", ratioOfTextUnderCurrentFontSize * 100, fontSizeAndCount.fontSize);
-        if (!firstTextLegibilityScale && ratioOfTextUnderCurrentFontSize >= firstTextLegibilityScaleRatio)
-            firstTextLegibilityScale = targetLegibilityFontSize / fontSizeAndCount.fontSize;
-        if (!secondTextLegibilityScale && ratioOfTextUnderCurrentFontSize >= secondTextLegibilityScaleRatio)
-            secondTextLegibilityScale = targetLegibilityFontSize / fontSizeAndCount.fontSize;
-    }
-
-    if (sortedFontSizesAndCounts.isEmpty()) {
-        firstTextLegibilityScale = fallbackTextLegibilityScale;
-        secondTextLegibilityScale = fallbackTextLegibilityScale;
-    } else if (secondTextLegibilityScale - firstTextLegibilityScale < minimumDifferenceBetweenTextLegibilityScales)
+        if (ratioOfTextUnderCurrentFontSize >= textLegibilityScaleRatio) {
+            textLegibilityScale = clampTo<double>(targetLegibilityFontSize / fontSizeAndCount.fontSize, viewportMinimumScale, viewportMaximumScale);
+            break;
+        }
+    }
+
+    auto firstTextLegibilityScale = std::min<double>(textLegibilityScale, defaultScale);
+    auto secondTextLegibilityScale = std::max<double>(textLegibilityScale, defaultScale);
+    if (secondTextLegibilityScale - firstTextLegibilityScale < minimumScaleDifferenceForZooming)
         firstTextLegibilityScale = secondTextLegibilityScale;
 
-    secondTextLegibilityScale = clampTo<double>(secondTextLegibilityScale, viewportMinimumScale, viewportMaximumScale);
-    firstTextLegibilityScale = clampTo<double>(firstTextLegibilityScale, viewportMinimumScale, viewportMaximumScale);
-
-    LOG(ViewGestures, "The computed text legibility scales are: (%.2f, %.2f)", firstTextLegibilityScale, secondTextLegibilityScale);
-
-    m_cachedTextLegibilityScales = std::optional<std::pair<double, double>> {{ firstTextLegibilityScale, secondTextLegibilityScale }};
+    m_cachedTextLegibilityScales.emplace(std::pair<double, double> { firstTextLegibilityScale, secondTextLegibilityScale });
     return m_cachedTextLegibilityScales;
 }