Add per-window resize-margin override (Hyprland's extend_border_grab_area)

MISSING.md had listed this as needing to touch srdwm_core::window::
hit_test's signature at every call site, including the honest-stub
Windows/macOS backends - overstated on closer inspection: that shared
function already takes a plain resize_margin: i32 parameter, agnostic
to where the value comes from. The only real change needed was reading
Window.resize_margin.unwrap_or(wm-wide default) instead of always the
WM-wide value, at the single call site inside WindowManager::hit_test
in core - no backend touched at all.

Window.resize_margin: Option<i32>, WindowRuleActions.resize_margin to
match, applied in add_window/reapply_rules_if_pending the same way
opacity already is. Settable via a rule action or
srd.window.set_resize_margin(n) on the focused window.

5 files changed, 34 insertions, 1 deletions

diff --git a/crates/core/src/manager/hittest.rs b/crates/core/src/manager/hittest.rs
index 2d52b57..06ac659 100644
--- a/crates/core/src/manager/hittest.rs
+++ b/crates/core/src/manager/hittest.rs
@@ -24,7 +24,8 @@ impl WindowManager {
             if w.minimized || w.workspace != self.current_workspace {
                 continue;
             }
-            if let Some(hit) = ResizeEdge::hit_test(w.geometry, x, y, w.decorated, w.border_width, self.resize_margin) {
+            let margin = w.resize_margin.unwrap_or(self.resize_margin);
+            if let Some(hit) = ResizeEdge::hit_test(w.geometry, x, y, w.decorated, w.border_width, margin) {
                 return Some((w.id, hit));
             }
         }
diff --git a/crates/core/src/manager/tests.rs b/crates/core/src/manager/tests.rs
index 24e8932..e1518f1 100644
--- a/crates/core/src/manager/tests.rs
+++ b/crates/core/src/manager/tests.rs
@@ -246,6 +246,23 @@
     }
 
     #[test]
+    fn per_window_resize_margin_overrides_the_wm_wide_default() {
+        // Hyprland's per-window `extend_border_grab_area` equivalent.
+        let mut wm = wm_with_monitor();
+        wm.set_layout(wm.current_workspace(), "tiling"); // keeps add_window from overriding geometry via SmartPlacement
+        let id = wm.alloc_window_id();
+        let mut w = Window::new(id, "a");
+        w.geometry = Rect::new(100, 100, 400, 300);
+        w.resize_margin = Some(30);
+        wm.add_window(w);
+
+        // 15px in from the left edge: well past the WM-wide default (6px),
+        // but still inside this window's own wider 30px override.
+        let hit = wm.hit_test(115, 250);
+        assert_eq!(hit.map(|(_, h)| h), Some(TitlebarHit::Resize(ResizeEdge::Left)));
+    }
+
+    #[test]
     fn moving_window_to_another_workspace_removes_it_from_current() {
         let mut wm = wm_with_monitor();
         let a = wm.alloc_window_id();
diff --git a/crates/core/src/manager/windows.rs b/crates/core/src/manager/windows.rs
index 6171c15..4b4c0c8 100644
--- a/crates/core/src/manager/windows.rs
+++ b/crates/core/src/manager/windows.rs
@@ -52,6 +52,9 @@ impl WindowManager {
             if let Some(opacity) = a.opacity {
                 window.opacity = opacity.clamp(0.0, 1.0);
             }
+            if let Some(margin) = a.resize_margin {
+                window.resize_margin = Some(margin);
+            }
         }
 
         if let Some(monitor) = self.primary_monitor() {
@@ -127,6 +130,9 @@ impl WindowManager {
         if let Some(opacity) = actions.opacity {
             window.opacity = opacity.clamp(0.0, 1.0);
         }
+        if let Some(margin) = actions.resize_margin {
+            window.resize_margin = Some(margin);
+        }
         if let Some(geometry) = actions.geometry {
             window.geometry = geometry;
         }
diff --git a/crates/core/src/rules.rs b/crates/core/src/rules.rs
index e0e87cb..7d9ee31 100644
--- a/crates/core/src/rules.rs
+++ b/crates/core/src/rules.rs
@@ -90,6 +90,9 @@ pub struct WindowRuleActions {
     pub pinned: Option<bool>,
     /// Content opacity, `0.0`..=`1.0` (Hyprland's `windowrule = opacity`).
     pub opacity: Option<f32>,
+    /// Per-window resize-grab-margin override, in logical pixels
+    /// (Hyprland's per-window `extend_border_grab_area`).
+    pub resize_margin: Option<i32>,
 }
 
 #[derive(Debug, Clone, Default)]
diff --git a/crates/core/src/window.rs b/crates/core/src/window.rs
index b79151d..850b936 100644
--- a/crates/core/src/window.rs
+++ b/crates/core/src/window.rs
@@ -97,6 +97,11 @@ pub struct Window {
     /// effect still keeps its frame legible. Set via `srd.window.
     /// set_opacity()` or a rule's `opacity` action.
     pub opacity: f32,
+    /// Per-window override of `WindowManager::resize_margin`, `None` to
+    /// just inherit it. Hyprland's `extend_border_grab_area` is per-window
+    /// (a `windowrule`); this is the equivalent, set via a rule's
+    /// `resize_margin` action or `srd.window.set_resize_margin()`.
+    pub resize_margin: Option<i32>,
     pub workspace: usize,
     pub monitor: u32,
     /// Whether `WindowManager`'s class/title-matched rules have already
@@ -143,6 +148,7 @@ impl Window {
             border_color: (136, 192, 208), // Nord accent, matches legacy theme default
             border_width: 2,
             opacity: 1.0,
+            resize_margin: None,
             workspace: 0,
             monitor: 0,
             rules_applied: false,