Piece dragging partially working

src/Main.cake

@@ -284,17 +284,21 @@
   (printf "%s\n" fogleman-board-string)
   (return true))
 
-(defun-local game-piece-position-to-screen-position (piece (* (const board-piece)) &return vec2)
+(defun-local game-piece-grid-position-to-screen-position (piece (* (const board-piece)) &return vec2)
   (var piece-position vec2 (array (type-cast (vec-x (path piece > grid-position)) float)
                                   (type-cast (vec-y (path piece > grid-position)) float)))
   ;; Transfer to pixel space
   (set piece-position (vec2-multiply (array (repeat g-game-board-cell-size-px)) piece-position))
-  ;; Add in moving position
-  (set piece-position (vec2-add piece-position (path piece > moving-position)))
   ;; Add board offset
   (set piece-position (vec2-add piece-position g-game-board-inner-top-left-px))
   (return piece-position))
 
+(defun-local game-piece-position-to-screen-position (piece (* (const board-piece)) &return vec2)
+  (var piece-position vec2 (game-piece-grid-position-to-screen-position piece))
+  ;; Add in moving position
+  (set piece-position (vec2-add piece-position (path piece > moving-position)))
+  (return piece-position))
+
 (defun-local game-piece-get-screen-size (piece (* (const board-piece)) &return vec2)
   (var piece-grid-size vec2
        (array
@@ -496,6 +500,7 @@ Rush Hour database from Michael Fogleman.\n\n")
   ;;
   ;; Game loop
   ;;
+  (var selected-piece (* board-piece) null)
   (var exit-reason (* (const char)) null)
   (while (not exit-reason)
     (var event SDL_Event)
@@ -508,9 +513,13 @@ Rush Hour database from Michael Fogleman.\n\n")
 
     (var mouse-x int 0)
     (var mouse-y int 0)
-    (var mouse-buttons Uint32 (SDL_GetMouseState (addr mouse-x) (addr mouse-y)))
+    (var mouse-button-state Uint32 (SDL_GetMouseState (addr mouse-x) (addr mouse-y)))
 
-    (var hovered-piece (* board-piece) (pick-game-piece-from-screen-position mouse-x mouse-y))
+    (if (bit-and mouse-button-state SDL_BUTTON_LMASK)
+        (block
+            (unless selected-piece ;; If holding, allow dragging even when not exactly on piece
+              (set selected-piece (pick-game-piece-from-screen-position mouse-x mouse-y))))
+        (set selected-piece nullptr))
 
     (SDL_RenderClear renderer)
     (unless (= 0 (SDL_RenderCopy renderer background-texture null null))
@@ -538,10 +547,17 @@ Rush Hour database from Michael Fogleman.\n\n")
 
     (on-each-existing-board-piece ;; Draw pieces
      piece piece-index
-     (when (= hovered-piece piece)
-       (continue))
-     (var piece-position vec2 (game-piece-position-to-screen-position piece))
+     (if (= selected-piece piece)
+         (scope
+          (var piece-position vec2 (game-piece-grid-position-to-screen-position piece))
+          (var mouse-board-pos vec2 (array (type-cast mouse-x float) (type-cast mouse-y float)))
+          (set mouse-board-pos (vec2-subtract mouse-board-pos piece-position))
+          (set (path piece > moving-position)
+               mouse-board-pos))
+         ;; Reset positions on release
+         (set (path piece > moving-position) (array 0)))
 
+     (var piece-position vec2 (game-piece-position-to-screen-position piece))
      (var piece-size vec2 (game-piece-get-screen-size piece))
 
      (var selected-piece-origin vec2 piece-2-1-origin)