Convert texture loading code to Zig

LodePNG replaces stb because complicated headers don't play nice with Zig.
Textures are now loaded from installed path instead of CWD too.

1 files changed, 73 insertions, 0 deletions

diff --git a/src/misc.zig b/src/misc.zig
new file mode 100644
index 0000000..ff45adc
--- /dev/null
+++ b/src/misc.zig
@@ -0,0 +1,73 @@
+// Miscellaneous functions
+// Copyright (C) 2021  Nguyễn Gia Phong
+//
+// This file is part of Black Shades.
+//
+// Black Shades is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published
+// by the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// Black Shades is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Black Shades.  If not, see <https://www.gnu.org/licenses/>.
+
+usingnamespace @cImport({
+    @cInclude("GL/gl.h");
+    @cInclude("GL/glu.h");
+    @cInclude("lodepng.h");
+});
+
+const allocator = std.heap.c_allocator;
+const cwd = std.fs.cwd;
+const data_dir = @import("build_options").data_dir;
+const free = std.c.free;
+const sep = std.fs.path.sep;
+const maxInt = std.math.maxInt;
+const std = @import("std");
+const span = std.mem.span;
+
+const max_size = maxInt(usize); // don't judge me, take care of me
+const texture_dir = data_dir ++ [_]u8{ sep } ++ "textures";
+
+fn check(errorString: fn (c_uint) callconv(.C) [*c]const u8,
+         status: anytype) void {
+    if (status != 0)
+        @panic(span(errorString(@intCast(c_uint, status))));
+}
+
+pub export fn loadTexture(filename: [*:0]const u8) GLuint {
+    var dir = cwd().openDir(texture_dir, .{}) catch unreachable;
+    defer dir.close();
+    var file = dir.readFileAlloc(allocator, span(filename), max_size)
+        catch unreachable;
+    defer allocator.free(file);
+
+    var data: [*c]u8 = undefined;
+    var w: c_uint = undefined;
+    var h: c_uint = undefined;
+    check(lodepng_error_text,
+          lodepng_decode32(&data, &w, &h, file.ptr, file.len));
+    defer free(data);
+
+    var texture: GLuint = undefined;
+    glGenTextures(1, &texture);
+    glBindTexture(GL_TEXTURE_2D, texture);
+    defer glBindTexture(GL_TEXTURE_2D, 0);
+    glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE);
+    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
+    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
+
+    const width = @intCast(GLint, w);
+    const height = @intCast(GLint, h);
+    glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
+    glTexImage2D(GL_TEXTURE_2D, 0, 4, width, height,
+                 0, GL_RGBA, GL_UNSIGNED_BYTE, data);
+    check(gluErrorString, gluBuild2DMipmaps(GL_TEXTURE_2D, 4, width, height,
+                                            GL_RGBA, GL_UNSIGNED_BYTE, data));
+    return texture;
+}