add viewer, the code sucks but it's 1AM and I yearn for my bed

build.zig

@@ -27,10 +27,28 @@ pub fn build(b: *std.Build) void {
     const run_cmd = b.addRunArtifact(exe);
     run_cmd.step.dependOn(b.getInstallStep());
 
-    if (b.args) |args| {
-        run_cmd.addArgs(args);
-    }
-
     const run_step = b.step("run", "Run the app");
     run_step.dependOn(&run_cmd.step);
+
+    // Viewer debug app
+
+    const viewer = b.addExecutable(.{
+        .name = "binfon-viewer",
+        .root_source_file = b.path("src/view.zig"),
+        .target = target,
+        .optimize = optimize,
+    });
+
+    b.installArtifact(viewer);
+
+    const view_cmd = b.addRunArtifact(viewer);
+    view_cmd.step.dependOn(b.getInstallStep());
+
+    const view_step = b.step("view", "Run the app");
+    view_step.dependOn(&view_cmd.step);
+
+    if (b.args) |args| {
+        run_cmd.addArgs(args);
+        view_cmd.addArgs(args);
+    }
 }

src/view.zig

@@ -0,0 +1,49 @@
+const std = @import("std");
+
+pub fn main() !void {
+    // Get allocator
+    var gpa = std.heap.GeneralPurposeAllocator(.{}){};
+    const allocator = gpa.allocator();
+    defer _ = gpa.deinit();
+
+    // Get args
+    const args = try std.process.argsAlloc(allocator);
+    defer std.process.argsFree(allocator, args);
+
+    std.debug.print("args: {s}\n", .{args});
+    if (args.len < 4) {
+        std.log.err("Usage: {s} <glyph width (eg. 8)> <glyph height (eg. 16)> <file.font.bin>", .{args[0]});
+        std.process.exit(1);
+    }
+
+    const bytesPerRow = (try std.fmt.parseInt(u8, args[1], 10)) / 8;
+    const glyphHeight = try std.fmt.parseInt(u8, args[2], 10);
+
+    // Open font
+    const file = try std.fs.cwd().openFile(args[3], .{});
+    defer file.close();
+
+    // Read byte by byte
+    var reader = file.reader();
+    var i: u16 = 0;
+    while (true) {
+        std.debug.print(" -- GLYPH {d} / 0x{x} --\n", .{ i, i });
+        for (0..glyphHeight) |y| {
+            for (0..bytesPerRow) |_| {
+                const next = try reader.readByte();
+                std.debug.print("{x}: ", .{y});
+                for (0..8) |x| {
+                    if (@as(u1, @truncate(next >> @truncate(8 - x))) == 1) {
+                        std.debug.print("*", .{});
+                    } else {
+                        std.debug.print(" ", .{});
+                    }
+                }
+                std.debug.print(" ", .{});
+            }
+            std.debug.print("\n", .{});
+        }
+
+        i += 1;
+    }
+}