Let a brush paint from the first frame of a stroke

Every stroke opened with an isolated dot: the press applied one dab, then
the 0.3s initial delay blocked the next 300ms of motion, so the line only
began well after the cursor had moved on.

Drop the concept rather than shorten it. Metal and grass already
overrode it to zero, so a brush now repeats purely at apply_delay(),
which scales with brush area and floors at 10ms.

Author: gajop

native/src/sbc/grass/brushes.rs

@@ -12,10 +12,6 @@ impl MapBrush for Grass {
     fn name(&self) -> &'static str {
         "grass"
     }
-    fn initial_delay(&self) -> f32 {
-        0.0
-    }
-
     fn prepare(
         &self,
         brush: &BrushSettings,

native/src/sbc/metal/brushes.rs

@@ -12,10 +12,6 @@ impl MapBrush for Metal {
     fn name(&self) -> &'static str {
         "metal"
     }
-    fn initial_delay(&self) -> f32 {
-        0.0
-    }
-
     fn prepare(
         &self,
         brush: &BrushSettings,

native/src/sbc/states/map_editing.rs

@@ -54,10 +54,6 @@ impl BrushButton {
 pub(crate) trait MapBrush: Sync {
     fn name(&self) -> &'static str;
 
-    fn initial_delay(&self) -> f32 {
-        0.3
-    }
-
     /// Whether the current domain settings can produce a command.
     fn is_ready(&self, _brush: &BrushSettings) -> bool {
         true
@@ -114,7 +110,6 @@ pub(crate) struct MapEditingState {
     /// Screen position paired with `last_hit`, in the ray-trace convention.
     last_screen: Option<(f32, f32)>,
     last_apply: Option<Instant>,
-    initial_delay_left: f32,
     preview: BrushPreview,
 }
 
@@ -128,7 +123,6 @@ impl MapEditingState {
             last_hit: None,
             last_screen: None,
             last_apply: None,
-            initial_delay_left: tool.initial_delay(),
             preview: BrushPreview::new(),
         }
     }
@@ -155,10 +149,8 @@ impl MapEditingState {
             self.last_apply = Some(now);
             return true;
         };
-        let delay = self.apply_delay().max(self.initial_delay_left);
-        if now.duration_since(last).as_secs_f32() >= delay {
+        if now.duration_since(last).as_secs_f32() >= self.apply_delay() {
             self.last_apply = Some(now);
-            self.initial_delay_left = 0.0;
             return true;
         }
         false
@@ -168,7 +160,6 @@ impl MapEditingState {
         if self.painting {
             return;
         }
-        self.initial_delay_left = self.tool.initial_delay();
         ctx.set_multiple_command_mode(true);
         self.painting = true;
     }