Click and drag on squares

2 files changed, 85 insertions, 12 deletions

diff --git a/engine b/engine
-Subproject e1ff0e3d124151c4c965f4d731c795d31732e42
+Subproject 9c224b99cda7331f4297bd58fa70a53b9de95c0
diff --git a/src/main.zig b/src/main.zig
index bebb189..cb1395d 100644
--- a/src/main.zig
+++ b/src/main.zig
@@ -23,13 +23,34 @@ const plane_verts = [_][2]f32{
     .{ 1, 1 },
 };
 
-var pos: [2]f32 = .{ 0, 0 };
-var push: bool = false;
+const Mouse = struct {
+    mutex: bool = false,
+    pos: [2]f32 = .{ 0, 0 },
+    down: bool = false,
+    was_down: bool = false,
+
+    //Note(Alaric): This is the most suspicious mutex of all time.
+    fn lock(self: *Mouse) void {
+        var l: ?bool = self.mutex;
+        while (l != null) {
+            l = @cmpxchgWeak(bool, &self.mutex, false, true, .seq_cst, .seq_cst);
+        }
+    }
+
+    fn unlock(self: *Mouse) void {
+        engine.assert(self.mutex == true);
+        self.mutex = false;
+    }
+};
+var mouse: Mouse = .{};
+var input_priority: u8 = 0;
 
 const p_count = 8;
-var p_idx: usize = 0;
 var points: [p_count][2]f32 = [1][2]f32{.{ 0, 0 }} ** p_count;
 
+var grab_idx: ?usize = null;
+var grab_offset: [2]f32 = undefined;
+
 pub fn init() void {
     prog = webgl.createGeneral2DSolidProgram() catch return;
     prog.use();
@@ -40,17 +61,51 @@ pub fn init() void {
 }
 
 pub fn update() void {
+    const m = blk: {
+        mouse.lock();
+        defer mouse.unlock();
+
+        const pressed = mouse.down and !mouse.was_down;
+        const released = !mouse.down and mouse.was_down;
+        mouse.was_down = mouse.down;
+        input_priority = 0;
+        break :blk .{
+            .down = mouse.down,
+            .pressed = pressed,
+            .released = released,
+            .pos = mouse.pos,
+        };
+    };
+
+    const m_vec: @Vector(2, f32) = m.pos;
+    if (m.pressed) {
+        for (points, 0..) |p, i| {
+            const bl: @Vector(2, f32) = p;
+            const tr = bl + @Vector(2, f32){ 50, 50 };
+            if (@reduce(.And, m_vec >= bl) and @reduce(.And, m_vec < tr)) {
+                grab_offset = m_vec - bl;
+                grab_idx = i;
+            }
+        }
+    } else if (m.released and grab_idx != null) {
+        points[grab_idx.?] = m_vec - grab_offset;
+        grab_idx = null;
+    } else if (grab_idx != null) {
+        points[grab_idx.?] = m_vec - grab_offset;
+    }
     const dims = webgl.getScreenSize();
     webgl.viewportToScreen();
     prog.setUniform(.projection, matrix.projectionMatrix2D(dims[0], dims[1]));
-    prog.setUniform(.color, .{ 1, 0, 0 });
-    if (push) {
-        prog.setUniform(.color, .{ 0, 0, 1 });
-    }
     webgl.clear(bg);
     buffer.bind(.array_buffer);
 
-    for (points) |p| {
+    for (points, 0..) |p, i| {
+        const is_grabbed = grab_idx != null and grab_idx.? == i;
+        if (is_grabbed) {
+            prog.setUniform(.color, .{ 0, 1, 0 });
+        } else {
+            prog.setUniform(.color, .{ 1, 0, 0 });
+        }
         const model = Mat3.translation(p).scaled(.{ 50, 50 });
         prog.setUniform(.model, model);
         webgl.drawArrays(.triangles, 0, 6);
@@ -60,14 +115,32 @@ pub fn update() void {
 pub fn handleInput(event: input.InputEvent) void {
     switch (event) {
         .mouse => |m| {
+            mouse.lock();
+            defer mouse.unlock();
+
+            // We prioritize positions of click/release over drag events
+            const down = m.buttons.left and input_priority < 2;
+            const pressed = down and !mouse.was_down;
+            const released = !down and mouse.was_down;
+            const prio: u8 = if (pressed) 2 else if (released) 1 else 0;
+            if (prio < input_priority) {
+                return;
+            }
+            input_priority = prio;
+
             const dims = webgl.getScreenSize();
 
             const world_pos = .{ m.pos[0], dims[1] - m.pos[1] };
-            if (m.buttons.left and !push) {
-                points[p_idx] = world_pos;
-                p_idx = (p_idx + 1) % p_count;
+            mouse.pos = world_pos;
+
+            mouse.down = m.buttons.left;
+            if (pressed) {
+                engine.print("Clicked {d:.2}, {d:.2}, delta: {any}", .{
+                    world_pos[0],
+                    world_pos[1],
+                    m.delta,
+                });
             }
-            push = m.buttons.left;
         },
     }
 }