display: coalesce movement updates to prevent notify storms; add head…

README.md

@@ -26,3 +26,13 @@ Run `meson` to configure the build environment and then `ninja` to build
 To install, use `ninja install`
 
     ninja install
+
+## Headless tests (no GUI required)
+
+This repository now includes a small, headless test suite that exercises the core layout logic (overlap resolution, edge adjacency, and origin normalization) without requiring GTK or a running compositor. This helps validate behavior even on single‑monitor or headless environments.
+
+To run tests after configuring the build directory:
+
+    meson test -C build --print-errorlogs
+
+You should see the `layout_logic` test pass. These tests simulate 3+ displays, overlap scenarios, and ensure the layout can be normalized and stays connected without crashes.

meson.build

@@ -30,3 +30,4 @@ config_file = configure_file(
 subdir('data')
 subdir('src')
 subdir('po')
+subdir('tests')

src/Widgets/DisplayWidget.vala

@@ -580,24 +580,65 @@ public class Display.DisplayWidget : Gtk.Box {
     }
 
     public void set_virtual_monitor_geometry (int x, int y, int width, int height) {
-        virtual_monitor.x = x;
-        virtual_monitor.y = y;
-        real_width = width;
-        real_height = height;
+        // Avoid redundant updates that can trigger unnecessary notify signals
+        bool changed = false;
+        if (virtual_monitor.x != x) {
+            virtual_monitor.x = x;
+            changed = true;
+        }
+        if (virtual_monitor.y != y) {
+            virtual_monitor.y = y;
+            changed = true;
+        }
+        if (real_width != width) {
+            real_width = width;
+            changed = true;
+        }
+        if (real_height != height) {
+            real_height = height;
+            changed = true;
+        }
 
-        queue_resize ();
+        if (changed) {
+            queue_resize ();
+        }
     }
 
     public void move_x (int dx) {
+        if (dx == 0) {
+            return;
+        }
         virtual_monitor.x += dx;
         queue_resize ();
     }
 
     public void move_y (int dy) {
+        if (dy == 0) {
+            return;
+        }
         virtual_monitor.y += dy;
         queue_resize ();
     }
 
+    // Move by dx,dy in a single notify batch to avoid re-entrant signal storms
+    public void move_by (int dx, int dy) {
+        if (dx == 0 && dy == 0) {
+            return;
+        }
+
+        // Freeze notify on the virtual monitor while applying both deltas
+        virtual_monitor.freeze_notify ();
+        if (dx != 0) {
+            virtual_monitor.x += dx;
+        }
+        if (dy != 0) {
+            virtual_monitor.y += dy;
+        }
+        virtual_monitor.thaw_notify ();
+
+        queue_resize ();
+    }
+
     public bool equals (DisplayWidget sibling) {
         return virtual_monitor.id == sibling.virtual_monitor.id;
     }

src/Widgets/DisplaysOverlay.vala

@@ -141,8 +141,9 @@ public class Display.DisplaysOverlay : Gtk.Box {
     // dx & dy are screen offsets from the start of dragging
     private void on_drag_update (double dx, double dy) {
         if (!only_display && dragging_display != null) {
-            dragging_display.move_x ((int) ((dx - prev_dx) / current_ratio));
-            dragging_display.move_y ((int) ((dy - prev_dy) / current_ratio));
+            var ddx = (int) ((dx - prev_dx) / current_ratio);
+            var ddy = (int) ((dy - prev_dy) / current_ratio);
+            dragging_display.move_by (ddx, ddy);
             prev_dx = dx;
             prev_dy = dy;
         }
@@ -456,8 +457,7 @@ public class Display.DisplaysOverlay : Gtk.Box {
                 }
             }
 
-            other_display_widget.move_x (-dx);
-            other_display_widget.move_y (-dy);
+            other_display_widget.move_by (-dx, -dy);
             moved = moved || dx != 0 || dy != 0;
             if (dx != 0 || dy != 0) {
                 align_edges (other_display_widget, moved, ++level);
@@ -580,8 +580,7 @@ public class Display.DisplaysOverlay : Gtk.Box {
                    }
                 }
 
-                other_display_widget.move_x (distance_x);
-                other_display_widget.move_y (distance_y);
+                other_display_widget.move_by (distance_x, distance_y);
                 check_intersects (other_display_widget, moved, ++level);
             }
 

tests/meson.build

@@ -0,0 +1,13 @@
+test_deps = [
+  dependency('glib-2.0'),
+  dependency('gee-0.8')
+]
+
+test_exe = executable(
+  'layout_tests',
+  files('test_layout.vala'),
+  dependencies: test_deps,
+  vala_args: ['--fatal-warnings']
+)
+
+test('layout_logic', test_exe)

tests/test_layout.vala

@@ -0,0 +1,163 @@
+/*
+ * Headless tests for layout logic (no GTK). We simulate a subset of the
+ * geometry algorithms used by DisplaysOverlay and VirtualMonitor to ensure
+ * correctness with 3+ monitors and edge/overlap cases.
+ */
+
+public class TestVM : GLib.Object {
+    public int x { get; set; }
+    public int y { get; set; }
+    public int w { get; set; }
+    public int h { get; set; }
+
+    public TestVM (int x, int y, int w, int h) {
+        this.x = x; this.y = y; this.w = w; this.h = h;
+    }
+}
+
+namespace Layout {
+    public void set_origin_zero (GLib.List<TestVM> vms) {
+        int min_x = int.MAX;
+        int min_y = int.MAX;
+        foreach (unowned var vm in vms) {
+            min_x = int.min (min_x, vm.x);
+            min_y = int.min (min_y, vm.y);
+        }
+        if (min_x == 0 && min_y == 0) return;
+        foreach (unowned var vm in vms) {
+            vm.x -= min_x; vm.y -= min_y;
+        }
+    }
+
+    public bool intersects (TestVM a, TestVM b, out int ovw, out int ovh) {
+        int ax2 = a.x + a.w, ay2 = a.y + a.h;
+        int bx2 = b.x + b.w, by2 = b.y + b.h;
+        ovw = int.max (0, int.min (ax2, bx2) - int.max (a.x, b.x));
+        ovh = int.max (0, int.min (ay2, by2) - int.max (a.y, b.y));
+        return ovw > 0 && ovh > 0;
+    }
+
+    // Resolve overlaps by moving B minimally away from A along smaller overlap axis
+    public bool resolve_overlap_once (TestVM a, TestVM b) {
+        int ovw, ovh;
+        if (!intersects (a, b, out ovw, out ovh)) return false;
+        if (ovw <= ovh) {
+            if (b.x < a.x) b.x -= ovw; else b.x += ovw;
+        } else {
+            if (b.y < a.y) b.y -= ovh; else b.y += ovh;
+        }
+        return true;
+    }
+
+    public void resolve_all_overlaps (GLib.List<TestVM> vms, uint max_iter = 16) {
+        uint iter = 0;
+        while (iter++ < max_iter) {
+            bool moved = false;
+            for (int i = 0; i < (int) vms.length (); i++) {
+                for (int j = i + 1; j < (int) vms.length (); j++) {
+                    moved = resolve_overlap_once (vms.nth_data (i), vms.nth_data (j)) || moved;
+                }
+            }
+            if (!moved) break;
+        }
+    }
+
+    public bool is_connected_pair (TestVM a, TestVM b) {
+        // Adjoin: touch on an edge (inclusive) without overlapping interior
+        bool x_adjacent = (a.x + a.w == b.x) || (b.x + b.w == a.x);
+        bool y_overlap = !(a.y + a.h <= b.y || b.y + b.h <= a.y);
+        bool y_adjacent = (a.y + a.h == b.y) || (b.y + b.h == a.y);
+        bool x_overlap = !(a.x + a.w <= b.x || b.x + b.w <= a.x);
+        return (x_adjacent && y_overlap) || (y_adjacent && x_overlap);
+    }
+
+    public bool is_connected_all (GLib.List<TestVM> vms) {
+        if (vms.length () <= 1) return true;
+    var seen = new GLib.HashTable<TestVM,bool> (GLib.direct_hash, GLib.direct_equal);
+    var queue = new GLib.Queue<TestVM> ();
+        var first = vms.nth_data (0);
+        seen.insert (first, true);
+        queue.push_tail (first);
+        while (!queue.is_empty ()) {
+            var cur = queue.pop_head ();
+            foreach (unowned var vm in vms) {
+                if (seen.lookup (vm)) continue;
+                if (is_connected_pair (cur, vm)) {
+                    seen.insert (vm, true);
+                    queue.push_tail (vm);
+                }
+            }
+        }
+        return seen.size () == vms.length ();
+    }
+}
+
+int failures = 0;
+void assert_true (bool cond, string msg) {
+    if (!cond) {
+        critical ("Assertion failed: %s", msg);
+        failures++;
+    }
+}
+
+int main (string[] args) {
+    // Test 1: Three displays, initially overlapping; resolve, normalize, and validate connectivity
+    var vms = new GLib.List<TestVM> ();
+    vms.append (new TestVM (0, 0, 1920, 1080));
+    vms.append (new TestVM (1800, 0, 1920, 1080)); // overlaps 120px on X
+    vms.append (new TestVM (3600, 100, 1280, 1024)); // slightly below and to the right
+
+    Layout.resolve_all_overlaps (vms);
+    Layout.set_origin_zero (vms);
+    int _ovw, _ovh;
+    assert_true (!Layout.intersects (vms.nth_data (0), vms.nth_data (1), out _ovw, out _ovh), "VM0/VM1 should not overlap after resolve");
+    assert_true (!Layout.intersects (vms.nth_data (1), vms.nth_data (2), out _ovw, out _ovh), "VM1/VM2 should not overlap after resolve");
+
+    // Expect connectivity after minor adjustments
+    assert_true (Layout.is_connected_all (vms), "All VMs should be connected");
+
+    // Test 2: Vertical stacking with same X, ensure normalization keeps origin at (0,0)
+    var v2 = new GLib.List<TestVM> ();
+    v2.append (new TestVM (100, 200, 1600, 900));
+    v2.append (new TestVM (100, 1100, 1600, 900));
+    Layout.set_origin_zero (v2);
+    assert_true (v2.nth_data (0).x == 0 && v2.nth_data (0).y == 0, "Origin normalized to (0,0)");
+    assert_true (v2.nth_data (1).x == 0 && v2.nth_data (1).y == 900, "Second stacked below first at y=height");
+
+    // Test 3: Edge adjacency detection
+    var a = new TestVM (0, 0, 100, 100);
+    var b = new TestVM (100, 10, 100, 50); // touches a's right edge
+    assert_true (Layout.is_connected_pair (a, b), "Edge adjacency should be connected");
+
+    // Test 4: Same Y alignment with exact adjacency across three displays
+    var t4 = new GLib.List<TestVM> ();
+    t4.append (new TestVM (0, 0, 1000, 800));
+    t4.append (new TestVM (1000, 0, 1000, 800));
+    t4.append (new TestVM (2000, 0, 1000, 800));
+    assert_true (!Layout.intersects (t4.nth_data (0), t4.nth_data (1), out _ovw, out _ovh), "T4: 0/1 no overlap");
+    assert_true (!Layout.intersects (t4.nth_data (1), t4.nth_data (2), out _ovw, out _ovh), "T4: 1/2 no overlap");
+    assert_true (Layout.is_connected_all (t4), "T4: all connected along same Y");
+
+    // Test 5: Same Y with overlaps; resolver should separate into no-overlap configuration and keep connectivity
+    var t5 = new GLib.List<TestVM> ();
+    t5.append (new TestVM (0, 0, 1000, 800));
+    t5.append (new TestVM (900, 0, 1000, 800)); // overlaps with first by 100px
+    t5.append (new TestVM (1900, 0, 1000, 800)); // overlaps with second by 0px (adjacent or slight overlap if math changes)
+    Layout.resolve_all_overlaps (t5);
+    assert_true (!Layout.intersects (t5.nth_data (0), t5.nth_data (1), out _ovw, out _ovh), "T5: 0/1 resolved");
+    assert_true (!Layout.intersects (t5.nth_data (1), t5.nth_data (2), out _ovw, out _ovh), "T5: 1/2 resolved");
+    assert_true (Layout.is_connected_all (t5), "T5: all connected after resolve");
+
+    // Test 6: Vertical stacking with same X (three displays)
+    var t6 = new GLib.List<TestVM> ();
+    t6.append (new TestVM (0, 0, 1200, 900));
+    t6.append (new TestVM (0, 900, 1200, 900));
+    t6.append (new TestVM (0, 1800, 1200, 900));
+    assert_true (!Layout.intersects (t6.nth_data (0), t6.nth_data (1), out _ovw, out _ovh), "T6: 0/1 stacked no overlap");
+    assert_true (!Layout.intersects (t6.nth_data (1), t6.nth_data (2), out _ovw, out _ovh), "T6: 1/2 stacked no overlap");
+    assert_true (Layout.is_connected_all (t6), "T6: stacked connected");
+
+    // If we reached here, all tests passed
+    if (failures == 0) message ("layout tests passed");
+    return failures == 0 ? 0 : 1;
+}