LibGfx: Make text painting better at aligning vector fonts vertically

This is achieved by simplifying the logic in TextLayout. We get rid
of all the various ways that the layout bounding rect can get cropped.
Then we make sure to use the right pixel metrics.

Finally we use the font's own line gap metrics instead of hard-coding 4.

The end result is that text painted with vector fonts now gets pretty
reasonable vertical alignment in most cases.

Userland/Libraries/LibGUI/Label.cpp

@@ -117,7 +117,7 @@ void Label::size_to_fit()
 
 int Label::text_calculated_preferred_height() const
 {
-    return static_cast<int>(ceilf(Gfx::TextLayout(font(), Utf8View { m_text }, text_rect().to_type<float>()).bounding_rect(Gfx::TextWrapping::Wrap, Gfx::Painter::LINE_SPACING).height()));
+    return static_cast<int>(ceilf(Gfx::TextLayout(font(), Utf8View { m_text }, text_rect().to_type<float>()).bounding_rect(Gfx::TextWrapping::Wrap).height()));
 }
 
 Optional<UISize> Label::calculated_preferred_size() const

Userland/Libraries/LibGfx/Painter.cpp

@@ -1518,11 +1518,6 @@ void draw_text_line(FloatRect const& a_rect, Utf8View const& text, Font const& f
         VERIFY_NOT_REACHED();
     }
 
-    if (is_vertically_centered_text_alignment(alignment)) {
-        auto distance_from_baseline_to_bottom = (font.pixel_size() - 1) - font.baseline();
-        rect.translate_by(0, distance_from_baseline_to_bottom / 2);
-    }
-
     auto point = rect.location();
     auto space_width = font.glyph_width(' ') + font.glyph_spacing();
 
@@ -1726,19 +1721,17 @@ void Painter::do_draw_text(FloatRect const& rect, Utf8View const& text, Font con
 
     TextLayout layout(font, text, rect);
 
-    auto line_height = font.pixel_size() + LINE_SPACING;
+    auto line_height = font.preferred_line_height();
 
-    auto lines = layout.lines(elision, wrapping, LINE_SPACING);
-    auto bounding_rect = layout.bounding_rect(wrapping, LINE_SPACING);
+    auto lines = layout.lines(elision, wrapping);
+    auto bounding_rect = layout.bounding_rect(wrapping);
 
     bounding_rect.align_within(rect, alignment);
-    bounding_rect.intersect(rect);
 
     for (size_t i = 0; i < lines.size(); ++i) {
         auto line = Utf8View { lines[i] };
 
         FloatRect line_rect { bounding_rect.x(), bounding_rect.y() + i * line_height, bounding_rect.width(), line_height };
-        line_rect.intersect(rect);
 
         TextDirection line_direction = get_text_direction(line);
         if (text_contains_bidirectional_text(line, line_direction)) { // Slow Path: The line contains mixed BiDi classes

Userland/Libraries/LibGfx/TextLayout.cpp

@@ -20,15 +20,15 @@ struct Block {
     Utf8View characters;
 };
 
-FloatRect TextLayout::bounding_rect(TextWrapping wrapping, int line_spacing) const
+FloatRect TextLayout::bounding_rect(TextWrapping wrapping) const
 {
-    auto lines = wrap_lines(TextElision::None, wrapping, line_spacing, FitWithinRect::No);
-    if (!lines.size()) {
+    auto lines = wrap_lines(TextElision::None, wrapping);
+    if (lines.is_empty()) {
         return {};
     }
 
     FloatRect bounding_rect = {
-        0, 0, 0, (lines.size() * (m_font.pixel_size() + line_spacing)) - line_spacing
+        0, 0, 0, (static_cast<float>(lines.size()) * (m_font_metrics.ascent + m_font_metrics.descent + m_font_metrics.line_gap)) - m_font_metrics.line_gap
     };
 
     for (auto& line : lines) {
@@ -40,7 +40,7 @@ FloatRect TextLayout::bounding_rect(TextWrapping wrapping, int line_spacing) con
     return bounding_rect;
 }
 
-Vector<DeprecatedString, 32> TextLayout::wrap_lines(TextElision elision, TextWrapping wrapping, int line_spacing, FitWithinRect fit_within_rect) const
+Vector<DeprecatedString, 32> TextLayout::wrap_lines(TextElision elision, TextWrapping wrapping) const
 {
     Vector<Block> blocks;
 
@@ -106,34 +106,16 @@ Vector<DeprecatedString, 32> TextLayout::wrap_lines(TextElision elision, TextWra
         });
     }
 
-    size_t max_lines_that_can_fit = 0;
-    if (m_rect.height() >= m_font.glyph_height()) {
-        // NOTE: If glyph height is 10 and line spacing is 1, we can fit a
-        // single line into a 10px rect and a 20px rect, but 2 lines into a
-        // 21px rect.
-        max_lines_that_can_fit = 1 + (m_rect.height() - m_font.glyph_height()) / (m_font.glyph_height() + line_spacing);
-    }
-
-    if (max_lines_that_can_fit == 0)
-        return {};
-
     Vector<DeprecatedString> lines;
     StringBuilder builder;
     float line_width = 0;
     size_t current_block = 0;
-    bool did_not_finish = false;
     for (Block& block : blocks) {
         switch (block.type) {
         case BlockType::Newline: {
             lines.append(builder.to_deprecated_string());
             builder.clear();
             line_width = 0;
-
-            if (lines.size() == max_lines_that_can_fit && fit_within_rect == FitWithinRect::Yes) {
-                did_not_finish = true;
-                goto blocks_processed;
-            }
-
             current_block++;
             continue;
         }
@@ -152,11 +134,6 @@ Vector<DeprecatedString, 32> TextLayout::wrap_lines(TextElision elision, TextWra
                 line_width = 0;
             }
 
-            if (lines.size() == max_lines_that_can_fit && fit_within_rect == FitWithinRect::Yes) {
-                did_not_finish = true;
-                goto blocks_processed;
-            }
-
             builder.append(block.characters.as_string());
             line_width += block_width;
             current_block++;
@@ -164,18 +141,15 @@ Vector<DeprecatedString, 32> TextLayout::wrap_lines(TextElision elision, TextWra
         }
     }
 
-blocks_processed:
-    if (!did_not_finish) {
     auto last_line = builder.to_deprecated_string();
     if (!last_line.is_empty())
         lines.append(last_line);
-    }
 
     switch (elision) {
     case TextElision::None:
         break;
     case TextElision::Right: {
-        lines.at(lines.size() - 1) = elide_text_from_right(Utf8View { lines.at(lines.size() - 1) }, did_not_finish);
+        lines.at(lines.size() - 1) = elide_text_from_right(Utf8View { lines.at(lines.size() - 1) });
         break;
     }
     }
@@ -183,10 +157,10 @@ blocks_processed:
     return lines;
 }
 
-DeprecatedString TextLayout::elide_text_from_right(Utf8View text, bool force_elision) const
+DeprecatedString TextLayout::elide_text_from_right(Utf8View text) const
 {
     float text_width = m_font.width(text);
-    if (force_elision || text_width > static_cast<unsigned>(m_rect.width())) {
+    if (text_width > static_cast<float>(m_rect.width())) {
         float ellipsis_width = m_font.width("..."sv);
         float current_width = ellipsis_width;
         size_t glyph_spacing = m_font.glyph_spacing();

Userland/Libraries/LibGfx/TextLayout.h

@@ -20,11 +20,6 @@
 
 namespace Gfx {
 
-enum class FitWithinRect {
-    Yes,
-    No
-};
-
 // FIXME: This currently isn't an ideal way of doing things; ideally, TextLayout
 // would be doing the rendering by painting individual glyphs. However, this
 // would regress our Unicode bidirectional text support. Therefore, fixing this
@@ -46,23 +41,25 @@ class TextLayout {
 public:
     TextLayout(Gfx::Font const& font, Utf8View const& text, FloatRect const& rect)
         : m_font(font)
+        , m_font_metrics(font.pixel_metrics())
         , m_text(text)
         , m_rect(rect)
     {
     }
 
-    Vector<DeprecatedString, 32> lines(TextElision elision, TextWrapping wrapping, int line_spacing) const
+    Vector<DeprecatedString, 32> lines(TextElision elision, TextWrapping wrapping) const
     {
-        return wrap_lines(elision, wrapping, line_spacing, FitWithinRect::Yes);
+        return wrap_lines(elision, wrapping);
     }
 
-    FloatRect bounding_rect(TextWrapping wrapping, int line_spacing) const;
+    FloatRect bounding_rect(TextWrapping) const;
 
 private:
-    Vector<DeprecatedString, 32> wrap_lines(TextElision, TextWrapping, int line_spacing, FitWithinRect) const;
-    DeprecatedString elide_text_from_right(Utf8View, bool force_elision) const;
+    Vector<DeprecatedString, 32> wrap_lines(TextElision, TextWrapping) const;
+    DeprecatedString elide_text_from_right(Utf8View) const;
 
     Font const& m_font;
+    FontPixelMetrics m_font_metrics;
     Utf8View m_text;
     FloatRect m_rect;
 };