feat: automatic DPI detection

build.zig

@@ -90,6 +90,8 @@ pub fn build(b: *std.Build) void {
     });
     exe.headerpad_max_install_names = true;
 
+    if (target.result.os.tag == .macos) exe.linkFramework("CoreGraphics");
+
     const deps = .{
         .vaxis = b.dependency("vaxis", .{ .target = target, .optimize = optimize }),
         .fzwatch = b.dependency("fzwatch", .{ .target = target, .optimize = optimize }),

docs/config.md

@@ -62,6 +62,7 @@ Because fancy-cat provides sensible defaults, you only need to specify the optio
     "scroll_step": 100.0,
     "retry_delay": 0.2,
     "timeout": 5.0,
+    "detect_dpi": true,
     "dpi": 96.0,
     "history": 1000
   },
@@ -208,7 +209,8 @@ The `General` section includes various display and timing settings.
 | `zoom_step` | Float | Zoom multiplier per keystroke |
 | `zoom_min` | Float | Minimum zoom level allowed |
 | `scroll_step` | Float (pixels) | Distance the viewport moves per scroll keystroke |
-| `dpi` | Float | Resolution used for 100% zoom calculation |
+| `detect_dpi` | Boolean | Enables pixel-density detection so that 100% zoom = actual size |
+| `dpi` | Float | Pixel density to use if `detect_dpi` is false, or fallback if detection fails |
 | `retry_delay` | Float (seconds) | Delay before retrying to load a document or render a page |
 | `timeout` | Float (seconds) | Maximum time to keep retrying before giving up on loading a document or rendering a page |
 | `history` | Integer | Maximum number of entries in command history |

src/config/Config.zig

@@ -88,6 +88,7 @@ pub const General = struct {
     retry_delay: f32 = 0.2,
     timeout: f32 = 5.0,
     // resolution
+    detect_dpi: bool = true,
     dpi: f32 = 96.0,
     // whole number (possibly 0)
     history: u32 = 1000,
@@ -119,6 +120,7 @@ pub const General = struct {
         general.scroll_step = parseType(f32, val.object, "scroll_step", allocator, general.scroll_step);
         general.retry_delay = parseType(f32, val.object, "retry_delay", allocator, general.retry_delay);
         general.timeout = parseType(f32, val.object, "timeout", allocator, general.timeout);
+        general.detect_dpi = parseType(bool, val.object, "detect_dpi", allocator, general.detect_dpi);
         general.dpi = parseType(f32, val.object, "dpi", allocator, general.dpi);
         general.history = parseType(u32, val.object, "history", allocator, general.history);
 

src/handlers/DocumentHandler.zig

@@ -76,8 +76,8 @@ pub fn zoomOut(self: *Self) void {
     self.pdf_handler.zoomOut();
 }
 
-pub fn setZoom(self: *Self, zoom_factor: f32) void {
-    self.pdf_handler.active_zoom = @max(zoom_factor, self.pdf_handler.config.general.zoom_min);
+pub fn setZoom(self: *Self, percent: f32) void {
+    self.pdf_handler.setZoom(percent);
 }
 
 pub fn toggleColor(self: *Self) void {

src/handlers/PdfHandler.zig

@@ -4,6 +4,8 @@ const fastb64z = @import("fastb64z");
 const vaxis = @import("vaxis");
 const Config = @import("../config/Config.zig");
 const types = @import("./types.zig");
+const Utilities = @import("../utilities/Utilities.zig");
+
 const c = @cImport({
     @cInclude("fitz-z.h");
     @cInclude("mupdf/fitz.h");
@@ -226,6 +228,13 @@ pub fn zoomOut(self: *Self) void {
     self.active_zoom /= self.config.general.zoom_step;
 }
 
+pub fn setZoom(self: *Self, percent: f32) void {
+    var dpi = self.config.general.dpi;
+    if (self.config.general.detect_dpi) dpi = Utilities.getDPI() orelse dpi;
+
+    self.active_zoom = @max(percent * dpi / 7200.0, self.config.general.zoom_min);
+}
+
 pub fn toggleColor(self: *Self) void {
     self.config.general.colorize = !self.config.general.colorize;
 }

src/modes/CommandMode.zig

@@ -140,10 +140,7 @@ fn handleZoom(self: *Self, cmd: []const u8) bool {
 
     const number_str = cmd[0 .. cmd.len - 1];
     if (std.fmt.parseFloat(f32, number_str)) |percent| {
-        // TODO detect DPI
-        const dpi = self.context.document_handler.pdf_handler.config.general.dpi;
-        const zoom_factor = (percent * dpi) / 7200.0;
-        self.context.document_handler.setZoom(zoom_factor);
+        self.context.document_handler.setZoom(percent);
         self.context.resetCurrentPage();
         return true;
     } else |_| {

src/utilities/Utilities.zig

@@ -0,0 +1,11 @@
+const builtin = @import("builtin");
+const utilities = struct {
+    pub const macos = @import("./macos.zig");
+};
+
+pub fn getDPI() ?f32 {
+    return switch (builtin.os.tag) {
+        .macos => utilities.macos.getDPI(),
+        else => null,
+    };
+}

src/utilities/macos.zig

@@ -0,0 +1,37 @@
+const std = @import("std");
+pub const c = @cImport({
+    @cInclude("CoreGraphics/CoreGraphics.h");
+});
+
+pub fn getDPI() ?f32 {
+    const display = getDisplay();
+
+    if (c.CGDisplayCopyDisplayMode(display)) |mode| {
+        defer c.CGDisplayModeRelease(mode);
+        const width_px = @as(f32, @floatFromInt(c.CGDisplayModeGetPixelWidth(mode)));
+        const width_mm = @as(f32, @floatCast(c.CGDisplayScreenSize(display).width));
+        if (width_mm != 0) return std.math.round(width_px / width_mm * 25.4);
+    }
+    return null;
+}
+
+fn getDisplay() c.CGDirectDisplayID {
+    const main_display = c.CGMainDisplayID();
+
+    var disp_count: u32 = 0;
+    if (c.CGGetActiveDisplayList(0, null, &disp_count) != c.kCGErrorSuccess or disp_count <= 1) return main_display;
+
+    const win_list = c.CGWindowListCopyWindowInfo(c.kCGWindowListOptionOnScreenOnly | c.kCGWindowListExcludeDesktopElements, c.kCGNullWindowID) orelse return main_display;
+    defer c.CFRelease(win_list);
+    if (c.CFArrayGetCount(win_list) == 0) return main_display;
+
+    const win = @as(c.CFDictionaryRef, @ptrCast(c.CFArrayGetValueAtIndex(win_list, 0)));
+    const win_bounds = c.CFDictionaryGetValue(win, c.kCGWindowBounds) orelse return main_display;
+    var win_rect: c.CGRect = undefined;
+    if (!c.CGRectMakeWithDictionaryRepresentation(@as(c.CFDictionaryRef, @ptrCast(win_bounds)), &win_rect)) return main_display;
+
+    var display: c.CGDirectDisplayID = 0;
+    if (c.CGGetDisplaysWithRect(win_rect, 1, &display, &disp_count) == c.kCGErrorSuccess and disp_count > 0) return display;
+
+    return main_display;
+}