1 files changed, 45 insertions, 0 deletions
diff --git a/packages/ext-window-field/src/geometry.cpp b/packages/ext-window-field/src/geometry.cpp
new file mode 100644
index 0000000..163f2ff
--- /dev/null
+++ b/packages/ext-window-field/src/geometry.cpp
@@ -0,0 +1,45 @@
+#include "geometry.hpp"
+
+#include <algorithm>
+
+namespace unbox::ext_window_field::geom {
+
+auto apply_drag(Box start, Handle handle, int dx, int dy, Limits lim) -> Box {
+    Box r = start;
+    switch (handle) {
+    case Handle::move:
+        r.x = start.x + dx;
+        r.y = start.y + dy;
+        break;
+    case Handle::resize_br:
+        // Right + bottom edges follow the pointer; top-left anchored.
+        r.w = std::max(lim.min_w, start.w + dx);
+        r.h = std::max(lim.min_h, start.h + dy);
+        break;
+    case Handle::resize_bl:
+        // Left + bottom edges follow; the RIGHT edge (start.x + start.w) and the
+        // top edge stay anchored. Compute the new width first (clamped), then
+        // place x so the right edge does not move.
+        r.w = std::max(lim.min_w, start.w - dx);
+        r.x = start.x + start.w - r.w;
+        r.h = std::max(lim.min_h, start.h + dy);
+        break;
+    }
+    return r;
+}
+
+auto clamp_to_field(Box b, int field_w, int field_h) -> Box {
+    if (field_w > 0) {
+        // Largest x that keeps the right edge inside; pin to 0 if the window is
+        // wider than the field. Then clamp the origin into [0, max_x].
+        const int max_x = std::max(0, field_w - b.w);
+        b.x = std::clamp(b.x, 0, max_x);
+    }
+    if (field_h > 0) {
+        const int max_y = std::max(0, field_h - b.h);
+        b.y = std::clamp(b.y, 0, max_y);
+    }
+    return b;
+}
+
+} // namespace unbox::ext_window_field::geom