From a5debc29a59b090ede6a3867b25f4c728e4c7fda Mon Sep 17 00:00:00 2001
From: Simon Naarmann <s.naarmann@gmail.com>
Date: Wed, 25 Jan 2023 00:25:52 +0100
Subject: [PATCH] Custom convertMaskToAlpha for #431

---
 src/basics/alleg5.d             | 39 +++++++++++++++++++++++++++++++++
 src/graphic/color.d             | 11 ----------
 src/graphic/cutbit.d            |  5 +++--
 src/graphic/internal/loadfile.d |  3 +--
 4 files changed, 43 insertions(+), 15 deletions(-)

diff --git a/src/basics/alleg5.d b/src/basics/alleg5.d
index 65deee66..eb2f1a58 100644
--- a/src/basics/alleg5.d
+++ b/src/basics/alleg5.d
@@ -124,6 +124,45 @@ Albit albitCreateSmoothlyScalable(in int xl, in int yl)
     bool isTargetBitmap(in Albit b) { return al_get_target_bitmap() == b; }
 }
 
+/*
+ * My custom variant of al_convert_mask_to_alpha to debug github issue #431:
+ * Magic pink won't become transparent on macOS (both Intel and ARM64)
+ */
+void convertPinkToAlpha(Albit bitmap)
+{
+    auto region = LockReadWrite(bitmap);
+    auto target = TargetBitmap(bitmap);
+    immutable xl = bitmap.xl;
+    immutable yl = bitmap.yl;
+    immutable Alcol transp = al_map_rgba(0, 0, 0, 0);
+    for (int y = 0; y < yl; y++) {
+        for (int x = 0; x < xl; x++) {
+            immutable Alcol pixel = al_get_pixel(bitmap, x, y);
+            if (pixel.r == 1f && pixel.g == 0f && pixel.b == 1f) {
+                al_put_pixel(x, y, transp);
+            }
+        }
+    }
+}
+
+/*
+ * The reason for above custom variant of al_convert_mask_to_alpha() is
+ * that A5's version compares colors with memcmp, but memcmp fails for float
+ * color components +0 and -0 which must compare equal as color components:
+ */
+unittest {
+    union Float {
+        float f;
+        ubyte[4] arr;
+    }
+    Float a;
+    Float b;
+    a.f = +0f;
+    b.f = -0f;
+    assert (a.f == b.f);
+    assert (a.arr != b.arr);
+}
+
 // The following structs implement RAII.
 struct TargetBitmap
 {
diff --git a/src/graphic/color.d b/src/graphic/color.d
index 2abccbaa..ae4573b2 100644
--- a/src/graphic/color.d
+++ b/src/graphic/color.d
@@ -1,7 +1,5 @@
 module graphic.color;
 
-import std.random;
-
 public import basics.alleg5 :
     Alcol,
     al_map_rgb, al_unmap_rgb, al_map_rgb_f, al_unmap_rgb_f,
@@ -40,15 +38,6 @@ void computeColors(in int r, in int g, in int b)
 }
 
 private class ColorPrivate {
-
-    @property Alcol random()
-    {
-        alias rnd = uniform01!float;
-        float[] arr = [rnd(), 0.7 + 0.3 * rnd(), 0.3 * rnd()];
-        arr.randomShuffle();
-        return al_map_rgb_f(arr[0], arr[1], arr[2]);
-    }
-
     // This can't be an alias to al_map_rgb because al_map_rgb expects ubytes.
     Alcol makecol(in int r, in int g, in int b)
     {
diff --git a/src/graphic/cutbit.d b/src/graphic/cutbit.d
index 18288377..5af95b79 100644
--- a/src/graphic/cutbit.d
+++ b/src/graphic/cutbit.d
@@ -79,8 +79,9 @@ public:
     {
         // Try loading the file. If not found, don't crash, but log.
         bitmap = al_load_bitmap(fn.stringForReading.toStringz);
-        if (bitmap)
-            al_convert_mask_to_alpha(bitmap, color.pink);
+        if (bitmap) {
+            bitmap.convertPinkToAlpha();
+        }
         this(bitmap, cut);
     }
 
diff --git a/src/graphic/internal/loadfile.d b/src/graphic/internal/loadfile.d
index 62d68b33..b7ace64d 100644
--- a/src/graphic/internal/loadfile.d
+++ b/src/graphic/internal/loadfile.d
@@ -10,7 +10,6 @@ import std.algorithm; // find
 import basics.alleg5;
 import basics.globals : dirDataBitmap;
 import file.filename;
-import graphic.color;
 import graphic.cutbit;
 import graphic.internal.getters;
 import graphic.internal.names;
@@ -33,7 +32,7 @@ do {
         return;
     }
     loadedCutbitMayBeScaled[id] = new Cutbit(fn, Cutbit.Cut.ifGridExists);
-    al_convert_mask_to_alpha(loadedCutbitMayBeScaled[id].albit, color.pink);
+    loadedCutbitMayBeScaled[id].albit.convertPinkToAlpha();
     if (id.needGuiRecoloring) {
         eidrecol(loadedCutbitMayBeScaled[id], 0);
     }