background: allow specifying the repeat interval

Useful if you want to add smaller items to your background layers
every so often; you can specify the distance between them and make
it independent of the item height.

config/src/background.rs

@@ -1,4 +1,4 @@
-use crate::{default_one_point_oh, Config, HsbTransform, RgbaColor};
+use crate::{default_one_point_oh, Config, Dimension, HsbTransform, RgbaColor};
 use luahelper::impl_lua_conversion_dynamic;
 use wezterm_dynamic::{FromDynamic, FromDynamicOptions, ToDynamic, Value};
 
@@ -64,9 +64,13 @@ pub struct BackgroundLayer {
 
     #[dynamic(default)]
     pub repeat_x: BackgroundRepeat,
+    #[dynamic(try_from = "crate::units::OptPixelUnit", default)]
+    pub repeat_x_size: Option<Dimension>,
 
     #[dynamic(default)]
     pub repeat_y: BackgroundRepeat,
+    #[dynamic(try_from = "crate::units::OptPixelUnit", default)]
+    pub repeat_y_size: Option<Dimension>,
 
     #[dynamic(default)]
     pub vertical_align: BackgroundVerticalAlignment,
@@ -111,6 +115,8 @@ impl BackgroundLayer {
             attachment: Default::default(),
             repeat_x: Default::default(),
             repeat_y: Default::default(),
+            repeat_x_size: None,
+            repeat_y_size: None,
             vertical_align: Default::default(),
             horizontal_align: Default::default(),
             width: BackgroundSize::Percent(100),
@@ -136,6 +142,7 @@ pub enum BackgroundSize {
     /// Stretches the image to a percentage of the background size
     /// as determined by the `origin` property.
     Percent(u8),
+    // FIXME: Dimension
 }
 
 impl Default for BackgroundSize {

config/src/units.rs

@@ -1,5 +1,26 @@
 use wezterm_dynamic::{FromDynamic, FromDynamicOptions, ToDynamic, Value};
 
+#[derive(Debug, Copy, Clone)]
+pub struct OptPixelUnit(Option<Dimension>);
+
+impl FromDynamic for OptPixelUnit {
+    fn from_dynamic(
+        value: &Value,
+        _options: FromDynamicOptions,
+    ) -> Result<Self, wezterm_dynamic::Error> {
+        match value {
+            Value::Null => Ok(Self(None)),
+            value => Ok(Self(Some(DefaultUnit::Pixels.from_dynamic_impl(value)?))),
+        }
+    }
+}
+
+impl Into<Option<Dimension>> for OptPixelUnit {
+    fn into(self) -> Option<Dimension> {
+        self.0
+    }
+}
+
 #[derive(Debug, Copy, Clone)]
 pub struct PixelUnit(Dimension);
 

wezterm-gui/src/termwindow/background.rs

@@ -4,7 +4,7 @@ use crate::Dimensions;
 use anyhow::Context;
 use config::{
     BackgroundLayer, BackgroundRepeat, BackgroundSize, BackgroundSource, ConfigHandle,
-    GradientOrientation,
+    DimensionContext, GradientOrientation,
 };
 use std::collections::HashMap;
 use std::sync::{Arc, Mutex};
@@ -343,6 +343,17 @@ impl crate::TermWindow {
         let tex_height = sprite.coords.height() as f32;
         let aspect = tex_width as f32 / tex_height as f32;
 
+        let h_context = DimensionContext {
+            dpi: self.dimensions.dpi as f32,
+            pixel_max: pixel_width,
+            pixel_cell: self.render_metrics.cell_size.width as f32,
+        };
+        let v_context = DimensionContext {
+            dpi: self.dimensions.dpi as f32,
+            pixel_max: pixel_height,
+            pixel_cell: self.render_metrics.cell_size.height as f32,
+        };
+
         // log::info!("tex {tex_width}x{tex_height} aspect={aspect}");
 
         // Compute the largest aspect-preserved size that will fill the space
@@ -385,30 +396,41 @@ impl crate::TermWindow {
             BackgroundSize::Contain => max_aspect_width as f32,
             BackgroundSize::Cover => min_aspect_width as f32,
             BackgroundSize::Length(n) => n as f32,
-            BackgroundSize::Percent(p) => (pixel_width as f32 * p as f32) / 100.,
+            BackgroundSize::Percent(p) => (pixel_width * p as f32) / 100.,
         };
 
         let height = match layer.def.height {
             BackgroundSize::Contain => max_aspect_height as f32,
             BackgroundSize::Cover => min_aspect_height as f32,
             BackgroundSize::Length(n) => n as f32,
-            BackgroundSize::Percent(p) => (pixel_height as f32 * p as f32) / 100.,
+            BackgroundSize::Percent(p) => (pixel_height * p as f32) / 100.,
         };
         let origin_x = pixel_width / -2.;
         let top_pixel = pixel_height / -2.;
         let mut origin_y = top_pixel;
 
+        let repeat_x = layer
+            .def
+            .repeat_x_size
+            .map(|size| size.evaluate_as_pixels(h_context))
+            .unwrap_or(width);
+        let repeat_y = layer
+            .def
+            .repeat_y_size
+            .map(|size| size.evaluate_as_pixels(v_context))
+            .unwrap_or(height);
+
         // log::info!("computed {width}x{height}");
         if let Some(factor) = layer.def.attachment.scroll_factor() {
             let distance = top as f32 * self.render_metrics.cell_size.height as f32 * factor;
-            let num_tiles = distance / height;
-            origin_y -= num_tiles.fract() * height;
+            let num_tiles = distance / repeat_y;
+            origin_y -= num_tiles.fract() * repeat_y;
         }
 
         let limit_y = top_pixel + pixel_height;
 
         for y_step in 0.. {
-            let offset_y = y_step as f32 * height;
+            let offset_y = y_step as f32 * repeat_y;
             let origin_y = origin_y + offset_y;
             if origin_y >= limit_y
                 || (y_step > 0 && layer.def.repeat_y == BackgroundRepeat::NoRepeat)
@@ -417,7 +439,7 @@ impl crate::TermWindow {
             }
 
             for x_step in 0.. {
-                let offset_x = x_step as f32 * width;
+                let offset_x = x_step as f32 * repeat_x;
                 if offset_x >= pixel_width
                     || (x_step > 0 && layer.def.repeat_x == BackgroundRepeat::NoRepeat)
                 {