Performance|libappfw: Rasterize long text content in the background

When preparing text for drawing, rasterize longer text content in
the TextDrawable background thread. This should yield improved
performance when the text rasterization is slow.

Previously rasterization was always done in the UI thread.

doomsday/sdk/libappfw/include/de/framework/fontlinewrapping.h

@@ -23,6 +23,7 @@
 
 #include <de/String>
 #include <de/Font>
+#include <de/Image>
 #include <de/Lockable>
 #include <de/shell/ILineWrapping>
 
@@ -65,6 +66,9 @@ class LIBAPPFW_PUBLIC FontLineWrapping : public Lockable, public shell::ILineWra
     void wrapTextToWidth(String const &text, int maxWidth);
     void wrapTextToWidth(String const &text, Font::RichFormat const &format, int maxWidth);
 
+    void rasterizeLines(Rangei const &lineRange);
+    void clearRasterizedLines() const;
+
     /**
      * Cancels the ongoing wrapping operation. This is useful when doing long wrapping
      * operations in the background. An exception is thrown from the ongoing 
@@ -129,6 +133,16 @@ class LIBAPPFW_PUBLIC FontLineWrapping : public Lockable, public shell::ILineWra
      */
     LineInfo const &lineInfo(int index) const;
 
+    /**
+     * Returns a rasterized version of a segment.
+     * Before calling this, segments must first be rasterized by calling
+     * rasterizeAllSegments().
+     *
+     * @param line     Line index.
+     * @param segment  Segment on the line.
+     */
+    Image rasterizedSegment(int line, int segment) const;
+
 private:
     DENG2_PRIVATE(d)
 };

doomsday/sdk/libappfw/src/fontlinewrapping.cpp

@@ -22,6 +22,7 @@
 
 #include "de/FontLineWrapping"
 #include "de/BaseGuiApp"
+#include <de/Image>
 
 #include <QMap>
 
@@ -64,6 +65,11 @@ DENG2_PIMPL_NOREF(FontLineWrapping)
     typedef QList<Line *> Lines;
     Lines lines;
 
+    struct RasterizedLine {
+        QList<Image> segmentImages;
+    };
+    QList<RasterizedLine> rasterized;
+
     int maxWidth;
     String text;                ///< Plain text.
     Font::RichFormat format;
@@ -90,6 +96,7 @@ DENG2_PIMPL_NOREF(FontLineWrapping)
     {
         qDeleteAll(lines);
         lines.clear();
+        rasterized.clear();
     }
 
     String rangeText(Rangei const &range) const
@@ -504,6 +511,12 @@ DENG2_PIMPL_NOREF(FontLineWrapping)
 
         return lineRange.end + extraLinesProduced;
     }
+
+    Image rasterizeSegment(LineInfo::Segment const &segment)
+    {
+        return font->rasterize(text  .substr  (segment.range),
+                               format.subRange(segment.range));
+    }
 };
 
 FontLineWrapping::FontLineWrapping() : d(new Impl)
@@ -578,7 +591,7 @@ void FontLineWrapping::wrapTextToWidth(String const &text, Font::RichFormat cons
     // When tabs are used, we must first determine the maximum width of each tab stop.
     if (d->containsTabs(Rangei(0, text.size())))
     {
-        d->indent = 0;
+        d->indent  = 0;
         d->tabStop = 0;
 
         // Divide the content into lines by newlines.
@@ -750,9 +763,52 @@ Vector2i FontLineWrapping::charTopLeftInPixels(int line, int charIndex)
 
 FontLineWrapping::LineInfo const &FontLineWrapping::lineInfo(int index) const
 {
+    DENG2_ASSERT(line >= 0 && line < d->lines.size());
     return d->lines[index]->info;
 }
 
+void FontLineWrapping::rasterizeLines(Rangei const &lineRange)
+{
+    d->rasterized.clear();
+
+    for (int i = 0; i < height(); ++i)
+    {
+        Impl::RasterizedLine rasterLine;
+        if (lineRange.contains(i))
+        {
+            LineInfo const &line = lineInfo(i);
+            for (int k = 0; k < line.segs.size(); ++k)
+            {
+                rasterLine.segmentImages << d->rasterizeSegment(line.segs.at(k));
+            }
+        }
+        d->rasterized << rasterLine;
+    }
+}
+
+void FontLineWrapping::clearRasterizedLines() const
+{
+    d->rasterized.clear();
+}
+
+Image FontLineWrapping::rasterizedSegment(int line, int segment) const
+{
+    DENG2_ASSERT(line >= 0);
+    if (line >= 0 && line < d->rasterized.size())
+    {
+        auto const &rasterLine = d->rasterized.at(line);
+        if (!rasterLine.segmentImages.isEmpty())
+        {
+            DENG2_ASSERT(segment >= 0 && segment < rasterLine.segmentImages.size());
+            return rasterLine.segmentImages.at(segment);
+        }
+    }
+    // Rasterize now, since it wasn't previously rasterized.
+    return d->rasterizeSegment(lineInfo(line).segs.at(segment));
+}
+
+//---------------------------------------------------------------------------------------
+
 int FontLineWrapping::LineInfo::highestTabStop() const
 {
     int stop = -1;

doomsday/sdk/libappfw/src/gltextcomposer.cpp

@@ -195,13 +195,8 @@ DENG2_PIMPL(GLTextComposer)
                         fgColor = format.style().richStyleColor(Font::RichFormat::NormalColor);
                     }
 
-                    // Set up the background color to be transparent with no
-                    // change of color in the alphablended smooth edges.
-                    Vector4ub bgColor = fgColor;
-                    bgColor.w = 0;
-
-                    seg.id = atlas->alloc(font->rasterize(seg.text, format.subRange(seg.range),
-                                                          fgColor, bgColor));
+                    Image const segmentImage = wraps->rasterizedSegment(i, k);
+                    seg.id = atlas->alloc(segmentImage.multiplied(fgColor));
                 }
                 line.segs << seg;
             }
@@ -217,6 +212,8 @@ DENG2_PIMPL(GLTextComposer)
             changed = true;
         }
 
+        wraps->clearRasterizedLines();
+
         DENG2_ASSERT(wraps->height() == lines.size());
 
         return changed;

doomsday/sdk/libappfw/src/textdrawable.cpp

@@ -175,6 +175,11 @@ DENG2_PIMPL(TextDrawable)
             // This is where most of the time will be spent:
             _wrapper->wrapTextToWidth(_wrapper->plainText, _wrapper->format, _width);
 
+            // Pre-rasterize the first lines of the text. The assumption is that
+            // longer text will only be visible after scrolling, so it will be
+            // rasterized as needed.
+            _wrapper->rasterizeLines(Rangei(0, 10)); // May also take a while...
+
             // Pass the finished wrapping to the owner.
             {
                 DENG2_GUARD(d);