66d80e2519
* Move texture allocation into epaint/egui proper * Add TextureHandle * egui_glow: cast using bytemuck instead of unsafe code * Optimize glium painter * Optimize WebGL * Add example of loading an image from file
101 lines
2.7 KiB
Rust
101 lines
2.7 KiB
Rust
use crate::image::AlphaImage;
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/// An 8-bit texture containing font data.
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#[derive(Clone, Default)]
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pub struct FontImage {
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/// e.g. a hash of the data. Use this to detect changes!
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/// If the texture changes, this too will change.
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pub version: u64,
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/// The actual image data.
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pub image: AlphaImage,
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}
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impl FontImage {
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#[inline]
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pub fn size(&self) -> [usize; 2] {
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self.image.size
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}
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#[inline]
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pub fn width(&self) -> usize {
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self.image.size[0]
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}
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#[inline]
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pub fn height(&self) -> usize {
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self.image.size[1]
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}
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}
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/// Contains font data in an atlas, where each character occupied a small rectangle.
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///
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/// More characters can be added, possibly expanding the texture.
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#[derive(Clone, Default)]
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pub struct TextureAtlas {
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image: FontImage,
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/// Used for when allocating new rectangles.
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cursor: (usize, usize),
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row_height: usize,
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}
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impl TextureAtlas {
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pub fn new(size: [usize; 2]) -> Self {
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Self {
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image: FontImage {
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version: 0,
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image: AlphaImage::new(size),
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},
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..Default::default()
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}
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}
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pub fn image(&self) -> &FontImage {
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&self.image
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}
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pub fn image_mut(&mut self) -> &mut FontImage {
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self.image.version += 1;
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&mut self.image
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}
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/// Returns the coordinates of where the rect ended up.
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pub fn allocate(&mut self, (w, h): (usize, usize)) -> (usize, usize) {
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/// On some low-precision GPUs (my old iPad) characters get muddled up
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/// if we don't add some empty pixels between the characters.
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/// On modern high-precision GPUs this is not needed.
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const PADDING: usize = 1;
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assert!(
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w <= self.image.width(),
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"Tried to allocate a {} wide glyph in a {} wide texture atlas",
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w,
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self.image.width()
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);
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if self.cursor.0 + w > self.image.width() {
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// New row:
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self.cursor.0 = 0;
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self.cursor.1 += self.row_height + PADDING;
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self.row_height = 0;
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}
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self.row_height = self.row_height.max(h);
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resize_to_min_height(&mut self.image.image, self.cursor.1 + self.row_height);
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let pos = self.cursor;
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self.cursor.0 += w + PADDING;
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self.image.version += 1;
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(pos.0 as usize, pos.1 as usize)
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}
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}
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fn resize_to_min_height(image: &mut AlphaImage, min_height: usize) {
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while min_height >= image.height() {
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image.size[1] *= 2; // double the height
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}
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if image.width() * image.height() > image.pixels.len() {
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image.pixels.resize(image.width() * image.height(), 0);
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}
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}
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