[skottie] Shaper downscale-to-fit vertical alignment mode

Introduce a new hybrid valign extension, kVisualDownscaleToFit (sk_vj: 4):

  - when the text shaped at the requested size fits within the box,
    center vertically (same as kVisualCenter)
  - otherwise, scale down until it fits (same as kVisualResizeToFit)

Change-Id: I8e096a49e2b87582e1bd42161657ec4ef561ebdf
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/235601
Reviewed-by: Ben Wagner <bungeman@google.com>
Commit-Queue: Florin Malita <fmalita@chromium.org>

modules/skottie/src/text/SkottieShaper.cpp

@@ -171,7 +171,6 @@ public:
             return box;
         };
 
-        // Only ShapeToFit cares about the result height, and it uses kVisualCenter.
         SkASSERT(!shaped_height || fDesc.fVAlign == Shaper::VAlign::kVisualCenter);
 
         // Perform additional adjustments based on VAlign.
@@ -197,6 +196,7 @@ public:
             v_offset = fBox.fBottom - extent_box().fBottom;
             break;
         case Shaper::VAlign::kVisualResizeToFit:
+        case Shaper::VAlign::kVisualDownscaleToFit:
             SkASSERT(false);
             break;
         }
@@ -406,16 +406,35 @@ Shaper::Result ShapeToFit(const SkString& txt, const Shaper::TextDesc& orig_desc
 
 Shaper::Result Shaper::Shape(const SkString& txt, const TextDesc& desc, const SkPoint& point,
                              const sk_sp<SkFontMgr>& fontmgr) {
-    return (desc.fVAlign == VAlign::kVisualResizeToFit) // makes no sense in point mode
+    return (desc.fVAlign == VAlign::kVisualResizeToFit ||
+            desc.fVAlign == VAlign::kVisualDownscaleToFit) // makes no sense in point mode
             ? Result()
             : ShapeImpl(txt, desc, SkRect::MakeEmpty().makeOffset(point.x(), point.y()), fontmgr);
 }
 
 Shaper::Result Shaper::Shape(const SkString& txt, const TextDesc& desc, const SkRect& box,
                              const sk_sp<SkFontMgr>& fontmgr) {
-    return (desc.fVAlign == VAlign::kVisualResizeToFit)
-            ? ShapeToFit(txt, desc, box, fontmgr)
-            : ShapeImpl(txt, desc, box, fontmgr);
+    if (desc.fVAlign == VAlign::kVisualResizeToFit) {
+        return ShapeToFit(txt, desc, box, fontmgr);
+    }
+
+    if (desc.fVAlign == VAlign::kVisualDownscaleToFit) {
+        auto adjusted_desc = desc;
+        adjusted_desc.fVAlign = VAlign::kVisualCenter;
+
+        float height;
+        auto result = ShapeImpl(txt, adjusted_desc, box, fontmgr, &height);
+
+        if (height <= box.height()) {
+            return result;
+        }
+
+        adjusted_desc.fVAlign = VAlign::kVisualResizeToFit;
+
+        return ShapeToFit(txt, adjusted_desc, box, fontmgr);
+    }
+
+    return ShapeImpl(txt, desc, box, fontmgr);
 }
 
 SkRect Shaper::Result::computeVisualBounds() const {

modules/skottie/src/text/SkottieShaper.h

@@ -63,6 +63,9 @@ public:
         kVisualBottom,
         // Resize the text such that the extent box fits (snuggly) in the text box.
         kVisualResizeToFit,
+        // Same kVisualResizeToFit if the text doesn't fit at the specified font size.
+        // Otherwise, same as kVisualCenter.
+        kVisualDownscaleToFit,
     };
 
     enum Flags : uint32_t {

modules/skottie/src/text/TextValue.cpp

@@ -72,14 +72,20 @@ bool ValueTraits<TextValue>::FromJSON(const skjson::Value& jv,
 
     // Skia vertical alignment extension "sk_vj":
     static constexpr Shaper::VAlign gVAlignMap[] = {
-        Shaper::VAlign::kVisualTop,         // 'sk_vj': 0
-        Shaper::VAlign::kVisualCenter,      // 'sk_vj': 1
-        Shaper::VAlign::kVisualBottom,      // 'sk_vj': 2
-        Shaper::VAlign::kVisualResizeToFit, // 'sk_vj': 3
+        Shaper::VAlign::kVisualTop,            // 'sk_vj': 0
+        Shaper::VAlign::kVisualCenter,         // 'sk_vj': 1
+        Shaper::VAlign::kVisualBottom,         // 'sk_vj': 2
+        Shaper::VAlign::kVisualResizeToFit,    // 'sk_vj': 3
+        Shaper::VAlign::kVisualDownscaleToFit, // 'sk_vj': 4
     };
     size_t sk_vj;
-    if (Parse((*jtxt)["sk_vj"], &sk_vj) && sk_vj < SK_ARRAY_COUNT(gVAlignMap)) {
-        v->fVAlign = gVAlignMap[sk_vj];
+    if (Parse((*jtxt)["sk_vj"], &sk_vj)) {
+        if (sk_vj < SK_ARRAY_COUNT(gVAlignMap)) {
+            v->fVAlign = gVAlignMap[sk_vj];
+        } else {
+            abuilder->log(Logger::Level::kWarning, nullptr,
+                          "Ignoring unknown 'sk_vj' value: %zu", sk_vj);
+        }
     }
 
     const auto& parse_color = [] (const skjson::ArrayValue* jcolor,