From 5f5d94c63f1f45ebfaca0d454fc73faab57b4114 Mon Sep 17 00:00:00 2001
From: David Thompson <dthompson2@worcester.edu>
Date: Thu, 19 Nov 2020 08:54:10 -0500
Subject: graphics: path: Allow model-view matrix to be applied to rendered
 path.

Every other type of rendering operation supports this, so paths should
be no different.  This type of transformation, unlike a transformation
applied at the canvas or painter level, can cause a non-smooth output
the matrix scales the result since it's transforming the geometry
as-is rather than building new geometry with all path points
transformed.
---
 chickadee/graphics/path.scm | 25 +++++++++++++++++--------
 1 file changed, 17 insertions(+), 8 deletions(-)

diff --git a/chickadee/graphics/path.scm b/chickadee/graphics/path.scm
index 6eca4ab..3500c15 100644
--- a/chickadee/graphics/path.scm
+++ b/chickadee/graphics/path.scm
@@ -76,6 +76,7 @@
             canvas?
             set-canvas-painter!
             set-canvas-matrix!
+            draw-canvas*
             draw-canvas))
 
 
@@ -1229,12 +1230,14 @@
                      #:function 'not-equal))
 
 (define *debug?* #f)
+(define *mvp* (make-null-matrix4))
 
 ;; TODO: gradients
-(define* (draw-filled-path filled-path)
+(define* (draw-filled-path filled-path matrix)
   (let ((counts (filled-path-counts filled-path))
         (offsets (filled-path-offsets filled-path))
         (n (filled-path-count filled-path)))
+    (matrix4-mult! *mvp* matrix (current-projection))
     ;; Wireframe debug mode.
     (when *debug?*
       (begin
@@ -1270,7 +1273,7 @@
                           (filled-path-stencil-vertex-array filled-path)
                           (u32vector-ref offsets i)
                           (u32vector-ref counts i)
-                          #:mvp (current-projection)
+                          #:mvp *mvp*
                           #:mode 0)
               (loop (+ i 1))))))
       ;; Render a quad with the stencil applied.  The quad is the size
@@ -1280,19 +1283,20 @@
         (with-blend-mode (filled-path-blend-mode filled-path)
           (gpu-apply (force path-shader)
                      (filled-path-quad-vertex-array filled-path)
-                     #:mvp (current-projection)
+                     #:mvp *mvp*
                      #:mode 0
                      #:color (filled-path-color filled-path)))))))
 
 ;; TODO: dashed stroke
 ;; TODO: miter styles and miter limit
-(define* (draw-stroked-path stroked-path)
+(define* (draw-stroked-path stroked-path matrix)
+  (matrix4-mult! *mvp* matrix (current-projection))
   (with-blend-mode (stroked-path-blend-mode stroked-path)
     (gpu-apply* (force path-shader)
                 (stroked-path-vertex-array stroked-path)
                 0
                 (stroked-path-index-count stroked-path)
-                #:mvp (current-projection)
+                #:mvp *mvp*
                 #:color (stroked-path-color stroked-path)
                 #:mode 1
                 #:feather (stroked-path-feather stroked-path)
@@ -1547,9 +1551,14 @@
     (set-canvas-painter! canvas painter)
     canvas))
 
-(define (draw-canvas canvas)
+(define (draw-canvas* canvas matrix)
   (array-list-for-each (lambda (i tesselation)
                          (if (filled-path? tesselation)
-                             (draw-filled-path tesselation)
-                             (draw-stroked-path tesselation)))
+                             (draw-filled-path tesselation matrix)
+                             (draw-stroked-path tesselation matrix)))
                        (canvas-tesselated-paths canvas)))
+
+(define %identity-matrix (make-identity-matrix4))
+
+(define (draw-canvas canvas)
+  (draw-canvas* canvas %identity-matrix))
-- 
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