From 3adbe82e079c0c07425fddf4c0fffc50feb2645f Mon Sep 17 00:00:00 2001
From: Antonio Vazquez <blendergit@gmail.com>
Date: Tue, 27 Dec 2022 10:01:37 +0100
Subject: [PATCH] GPencil: Extract function to calculate cursor size

This function will be used in other areas of Blender.
---
 .../blender/editors/gpencil/gpencil_utils.c   | 78 ++++++++++++-------
 source/blender/editors/include/ED_gpencil.h   |  5 ++
 2 files changed, 56 insertions(+), 27 deletions(-)

diff --git a/source/blender/editors/gpencil/gpencil_utils.c b/source/blender/editors/gpencil/gpencil_utils.c
index 9f6b17b66e2..f8e2a8fd080 100644
--- a/source/blender/editors/gpencil/gpencil_utils.c
+++ b/source/blender/editors/gpencil/gpencil_utils.c
@@ -1730,6 +1730,56 @@ static bool gpencil_brush_cursor_poll(bContext *C)
   return false;
 }
 
+float ED_gpencil_cursor_radius(bContext *C, int x, int y)
+{
+  Scene *scene = CTX_data_scene(C);
+  Object *ob = CTX_data_active_object(C);
+  ARegion *region = CTX_wm_region(C);
+  Brush *brush = brush = scene->toolsettings->gp_paint->paint.brush;
+  bGPdata *gpd = ED_gpencil_data_get_active(C);
+
+  /* Show brush size. */
+  tGPspoint point2D;
+  float p1[3];
+  float p2[3];
+  float distance;
+  float radius = 2.0f;
+
+  if (ELEM(NULL, gpd, brush)) {
+    return radius;
+  }
+
+  /* Strokes in screen space or world space? */
+  if ((gpd->flag & GP_DATA_STROKE_KEEPTHICKNESS) != 0) {
+    /* In screen space the cursor radius matches the brush size. */
+    radius = (float)brush->size * 0.5f;
+  }
+  else {
+    /* To calculate the brush size in world space, we have to establish the zoom level.
+     * For this we take two 2D screen coordinates with a fixed offset,
+     * convert them to 3D coordinates and measure the offset distance in 3D.
+     * A small distance means a high zoom level. */
+    point2D.m_xy[0] = (float)x;
+    point2D.m_xy[1] = (float)y;
+    gpencil_stroke_convertcoords_tpoint(scene, region, ob, &point2D, NULL, p1);
+    point2D.m_xy[0] = (float)(x + 64);
+    gpencil_stroke_convertcoords_tpoint(scene, region, ob, &point2D, NULL, p2);
+    /* Clip extreme zoom level (and avoid division by zero). */
+    distance = MAX2(len_v3v3(p1, p2), 0.001f);
+
+    /* Handle layer thickness change. */
+    float brush_size = (float)brush->size;
+    bGPDlayer *gpl = BKE_gpencil_layer_active_get(gpd);
+    if (gpl != NULL) {
+      brush_size = MAX2(1.0f, brush_size + gpl->line_change);
+    }
+
+    /* Convert the 3D offset distance to a brush radius. */
+    radius = (1 / distance) * 2.0f * gpd->pixfactor * (brush_size / 64);
+  }
+  return radius;
+}
+
 /**
  * Helper callback for drawing the cursor itself.
  */
@@ -1813,39 +1863,13 @@ static void gpencil_brush_cursor_draw(bContext *C, int x, int y, void *customdat
           copy_v3_v3(color, is_vertex_stroke ? brush->rgb : gp_style->stroke_rgba);
         }
         else {
-          /* Show brush size. */
-          tGPspoint point2D;
-          float p1[3];
-          float p2[3];
-          float distance;
-
           /* Strokes in screen space or world space? */
           if ((gpd->flag & GP_DATA_STROKE_KEEPTHICKNESS) != 0) {
             /* In screen space the cursor radius matches the brush size. */
             radius = (float)brush->size * 0.5f;
           }
           else {
-            /* To calculate the brush size in world space, we have to establish the zoom level.
-             * For this we take two 2D screen coordinates with a fixed offset,
-             * convert them to 3D coordinates and measure the offset distance in 3D.
-             * A small distance means a high zoom level. */
-            point2D.m_xy[0] = (float)x;
-            point2D.m_xy[1] = (float)y;
-            gpencil_stroke_convertcoords_tpoint(scene, region, ob, &point2D, NULL, p1);
-            point2D.m_xy[0] = (float)(x + 64);
-            gpencil_stroke_convertcoords_tpoint(scene, region, ob, &point2D, NULL, p2);
-            /* Clip extreme zoom level (and avoid division by zero). */
-            distance = MAX2(len_v3v3(p1, p2), 0.001f);
-
-            /* Handle layer thickness change. */
-            float brush_size = (float)brush->size;
-            bGPDlayer *gpl = BKE_gpencil_layer_active_get(gpd);
-            if (gpl != NULL) {
-              brush_size = MAX2(1.0f, brush_size + gpl->line_change);
-            }
-
-            /* Convert the 3D offset distance to a brush radius. */
-            radius = (1 / distance) * 2.0f * gpd->pixfactor * (brush_size / 64);
+            radius = ED_gpencil_cursor_radius(C, x, y);
           }
 
           copy_v3_v3(color, is_vertex_stroke ? brush->rgb : gp_style->stroke_rgba);
diff --git a/source/blender/editors/include/ED_gpencil.h b/source/blender/editors/include/ED_gpencil.h
index 45e61592424..129229a8861 100644
--- a/source/blender/editors/include/ED_gpencil.h
+++ b/source/blender/editors/include/ED_gpencil.h
@@ -641,6 +641,11 @@ struct bGPDstroke *ED_gpencil_stroke_join_and_trim(struct bGPdata *gpd,
  */
 void ED_gpencil_stroke_close_by_distance(struct bGPDstroke *gps, float threshold);
 
+/**
+ * Calculate the brush cursor size in world space.
+ */
+float ED_gpencil_cursor_radius(struct bContext *C, int x, int y);
+
 #ifdef __cplusplus
 }
 #endif