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Add control of line height and letter spacing (#3302)

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* Add `TextFormat::extra_letter_spacing`

* Add control of line height

* Add to text layout demo

* Move the text layout demo to its own window in the demo app

* Fix doclink

* Better document points vs pixels

* Better documentation and code cleanup
This commit is contained in:
Emil Ernerfeldt
2023-09-05 10:45:11 +02:00
committed by GitHub
parent cf163cc954
commit 46ea72abe4
13 changed files with 286 additions and 113 deletions
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9
crates/epaint/src/text/font.rs
View File

@@ -49,11 +49,6 @@ pub struct GlyphInfo {
/// Unit: points.
pub ascent: f32,
/// row height computed from the font metrics.
///
/// Unit: points.
pub row_height: f32,
/// Texture coordinates.
pub uv_rect: UvRect,
}
@@ -65,7 +60,6 @@ impl Default for GlyphInfo {
id: ab_glyph::GlyphId(0),
advance_width: 0.0,
ascent: 0.0,
row_height: 0.0,
uv_rect: Default::default(),
}
}
@@ -250,7 +244,7 @@ impl FontImpl {
/ self.pixels_per_point
}
/// Height of one row of text. In points
/// Height of one row of text in points.
#[inline(always)]
pub fn row_height(&self) -> f32 {
self.height_in_points
@@ -312,7 +306,6 @@ impl FontImpl {
id: glyph_id,
advance_width: advance_width_in_points,
ascent: self.ascent,
row_height: self.row_height(),
uv_rect,
}
}

2
crates/epaint/src/text/fonts.rs
View File

@@ -653,7 +653,7 @@ impl FontsImpl {
self.font(font_id).has_glyphs(s)
}
/// Height of one row of text. In points
/// Height of one row of text in points.
fn row_height(&mut self, font_id: &FontId) -> f32 {
self.font(font_id).row_height()
}

53
crates/epaint/src/text/text_layout.rs
View File

@@ -113,11 +113,15 @@ fn layout_section(
format,
} = section;
let font = fonts.font(&format.font_id);
let font_height = font.row_height();
let line_height = section
.format
.line_height
.unwrap_or_else(|| font.row_height());
let extra_letter_spacing = section.format.extra_letter_spacing;
let mut paragraph = out_paragraphs.last_mut().unwrap();
if paragraph.glyphs.is_empty() {
paragraph.empty_paragraph_height = font_height; // TODO(emilk): replace this hack with actually including `\n` in the glyphs?
paragraph.empty_paragraph_height = line_height; // TODO(emilk): replace this hack with actually including `\n` in the glyphs?
}
paragraph.cursor_x += leading_space;
@@ -128,19 +132,20 @@ fn layout_section(
if job.break_on_newline && chr == '\n' {
out_paragraphs.push(Paragraph::default());
paragraph = out_paragraphs.last_mut().unwrap();
paragraph.empty_paragraph_height = font_height; // TODO(emilk): replace this hack with actually including `\n` in the glyphs?
paragraph.empty_paragraph_height = line_height; // TODO(emilk): replace this hack with actually including `\n` in the glyphs?
} else {
let (font_impl, glyph_info) = font.glyph_info_and_font_impl(chr);
if let Some(font_impl) = font_impl {
if let Some(last_glyph_id) = last_glyph_id {
paragraph.cursor_x += font_impl.pair_kerning(last_glyph_id, glyph_info.id);
paragraph.cursor_x += extra_letter_spacing;
}
}
paragraph.glyphs.push(Glyph {
chr,
pos: pos2(paragraph.cursor_x, f32::NAN),
size: vec2(glyph_info.advance_width, glyph_info.row_height),
size: vec2(glyph_info.advance_width, line_height),
ascent: glyph_info.ascent,
uv_rect: glyph_info.uv_rect,
section_index,
@@ -328,8 +333,12 @@ fn replace_last_glyph_with_overflow_character(
};
let section = &job.sections[last_glyph.section_index as usize];
let extra_letter_spacing = section.format.extra_letter_spacing;
let font = fonts.font(&section.format.font_id);
let font_height = font.row_height();
let line_height = section
.format
.line_height
.unwrap_or_else(|| font.row_height());
let prev_glyph_id = prev_glyph.map(|prev_glyph| {
let (_, prev_glyph_info) = font.glyph_info_and_font_impl(prev_glyph.chr);
@@ -338,23 +347,29 @@ fn replace_last_glyph_with_overflow_character(
// undo kerning with previous glyph
let (font_impl, glyph_info) = font.glyph_info_and_font_impl(last_glyph.chr);
last_glyph.pos.x -= font_impl
.zip(prev_glyph_id)
.map(|(font_impl, prev_glyph_id)| font_impl.pair_kerning(prev_glyph_id, glyph_info.id))
.unwrap_or_default();
last_glyph.pos.x -= extra_letter_spacing
+ font_impl
.zip(prev_glyph_id)
.map(|(font_impl, prev_glyph_id)| {
font_impl.pair_kerning(prev_glyph_id, glyph_info.id)
})
.unwrap_or_default();
// replace the glyph
last_glyph.chr = overflow_character;
let (font_impl, glyph_info) = font.glyph_info_and_font_impl(last_glyph.chr);
last_glyph.size = vec2(glyph_info.advance_width, font_height);
last_glyph.size = vec2(glyph_info.advance_width, line_height);
last_glyph.uv_rect = glyph_info.uv_rect;
last_glyph.ascent = glyph_info.ascent;
// reapply kerning
last_glyph.pos.x += font_impl
.zip(prev_glyph_id)
.map(|(font_impl, prev_glyph_id)| font_impl.pair_kerning(prev_glyph_id, glyph_info.id))
.unwrap_or_default();
last_glyph.pos.x += extra_letter_spacing
+ font_impl
.zip(prev_glyph_id)
.map(|(font_impl, prev_glyph_id)| {
font_impl.pair_kerning(prev_glyph_id, glyph_info.id)
})
.unwrap_or_default();
row.rect.max.x = last_glyph.max_x();
@@ -474,7 +489,7 @@ fn galley_from_rows(
let mut min_x: f32 = 0.0;
let mut max_x: f32 = 0.0;
for row in &mut rows {
let mut row_height = first_row_min_height.max(row.rect.height());
let mut line_height = first_row_min_height.max(row.rect.height());
let mut row_ascent = 0.0f32;
first_row_min_height = 0.0;
@@ -484,10 +499,10 @@ fn galley_from_rows(
.iter()
.max_by(|a, b| a.size.y.partial_cmp(&b.size.y).unwrap())
{
row_height = glyph.size.y;
line_height = glyph.size.y;
row_ascent = glyph.ascent;
}
row_height = point_scale.round_to_pixel(row_height);
line_height = point_scale.round_to_pixel(line_height);
// Now positions each glyph:
for glyph in &mut row.glyphs {
@@ -503,11 +518,11 @@ fn galley_from_rows(
}
row.rect.min.y = cursor_y;
row.rect.max.y = cursor_y + row_height;
row.rect.max.y = cursor_y + line_height;
min_x = min_x.min(row.rect.min.x);
max_x = max_x.max(row.rect.max.x);
cursor_y += row_height;
cursor_y += line_height;
cursor_y = point_scale.round_to_pixel(cursor_y);
}

55
crates/epaint/src/text/text_layout_types.rs
View File

@@ -221,11 +221,28 @@ impl std::hash::Hash for LayoutSection {
// ----------------------------------------------------------------------------
#[derive(Clone, Debug, Hash, PartialEq)]
/// Formatting option for a section of text.
#[derive(Clone, Debug, PartialEq)]
#[cfg_attr(feature = "serde", derive(serde::Deserialize, serde::Serialize))]
pub struct TextFormat {
pub font_id: FontId,
/// Extra spacing between letters, in points.
///
/// Default: 0.0.
///
/// For even text it is recommended you round this to an even number of _pixels_.
pub extra_letter_spacing: f32,
/// Explicit line height of the text in points.
///
/// This is the distance between the bottom row of two subsequent lines of text.
///
/// If `None` (the default), the line height is determined by the font.
///
/// For even text it is recommended you round this to an even number of _pixels_.
pub line_height: Option<f32>,
/// Text color
pub color: Color32,
@@ -248,6 +265,8 @@ impl Default for TextFormat {
fn default() -> Self {
Self {
font_id: FontId::default(),
extra_letter_spacing: 0.0,
line_height: None,
color: Color32::GRAY,
background: Color32::TRANSPARENT,
italics: false,
@@ -258,6 +277,34 @@ impl Default for TextFormat {
}
}
impl std::hash::Hash for TextFormat {
#[inline]
fn hash<H: std::hash::Hasher>(&self, state: &mut H) {
let Self {
font_id,
extra_letter_spacing,
line_height,
color,
background,
italics,
underline,
strikethrough,
valign,
} = self;
font_id.hash(state);
crate::f32_hash(state, *extra_letter_spacing);
if let Some(line_height) = *line_height {
crate::f32_hash(state, line_height);
}
color.hash(state);
background.hash(state);
italics.hash(state);
underline.hash(state);
strikethrough.hash(state);
valign.hash(state);
}
}
impl TextFormat {
#[inline]
pub fn simple(font_id: FontId, color: Color32) -> Self {
@@ -486,10 +533,12 @@ pub struct Glyph {
/// `ascent` value from the font
pub ascent: f32,
/// Advance width and font row height.
/// Advance width and line height.
///
/// Does not control the visual size of the glyph (see [`Self::uv_rect`] for that).
pub size: Vec2,
/// Position of the glyph in the font texture, in texels.
/// Position and size of the glyph in the font texture, in texels.
pub uv_rect: UvRect,
/// Index into [`LayoutJob::sections`]. Decides color etc.