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[WIP PR] More pango examples #16

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2 changes: 2 additions & 0 deletions build.zig
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Original file line number Diff line number Diff line change
Expand Up @@ -25,7 +25,9 @@ const EXAMPLES = [_][]const u8{
"image_pattern",
"mask",
"multi_segment_caps",
"pango_shape",
"pango_simple",
"pango_twisted",
"rounded_rectangle",
"save_and_restore",
"set_line_cap",
Expand Down
187 changes: 187 additions & 0 deletions examples/pango_shape.zig
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Original file line number Diff line number Diff line change
@@ -0,0 +1,187 @@
//! Example code to show how to use pangocairo to render arbitrary shapes inside
//! a text layout, positioned by Pango.
//! https://gitlab.gnome.org/GNOME/pango/-/blob/master/examples/cairoshape.c
const std = @import("std");
const log = std.log;
const pi = std.math.pi;
const cos = std.math.cos;
const cairo = @import("cairo");
const pc = @import("pangocairo");

const BULLET = "•";

const text =
\\The GNOME project provides two things:
\\
\\ • The GNOME desktop environment
\\ • The GNOME development platform
\\ • Planet GNOME
;

const path =
\\M 86.068,1 C 61.466,0 56.851,35.041 70.691,35.041 C 84.529,35.041 110.671,0 86.068,0 z
\\M 45.217,30.699 C 52.586,31.149 60.671,2.577 46.821,4.374 C 32.976,6.171 37.845,30.249 45.217,30.699 z
\\M 11.445,48.453 C 16.686,46.146 12.12,23.581 3.208,29.735 C -5.7,35.89 6.204,50.759 11.445,48.453 z
\\M 26.212,36.642 C 32.451,35.37 32.793,9.778 21.667,14.369 C 10.539,18.961 19.978,37.916 26.212,36.642 L 26.212,36.642 z
\\M 58.791,93.913 C 59.898,102.367 52.589,106.542 45.431,101.092 C 22.644,83.743 83.16,75.088 79.171,51.386 C 75.86,31.712 15.495,37.769 8.621,68.553 C 3.968,89.374 27.774,118.26 52.614,118.26 C 64.834,118.26 78.929,107.226 81.566,93.248 C 83.58,82.589 57.867,86.86 58.791,93.913 L 58.791,93.913 z
;

// I don't know if the multiline string works or I have to use a single string
// const path = "M 86.068,1 C 61.466,0 56.851,35.041 70.691,35.041 C 84.529,35.041 110.671,0 86.068,0 z M 45.217,30.699 C 52.586,31.149 60.671,2.577 46.821,4.374 C 32.976,6.171 37.845,30.249 45.217,30.699 z M 11.445,48.453 C 16.686,46.146 12.12,23.581 3.208,29.735 C -5.7,35.89 6.204,50.759 11.445,48.453 z M 26.212,36.642 C 32.451,35.37 32.793,9.778 21.667,14.369 C 10.539,18.961 19.978,37.916 26.212,36.642 L 26.212,36.642 z M 58.791,93.913 C 59.898,102.367 52.589,106.542 45.431,101.092 C 22.644,83.743 83.16,75.088 79.171,51.386 C 75.86,31.712 15.495,37.769 8.621,68.553 C 3.968,89.374 27.774,118.26 52.614,118.26 C 64.834,118.26 78.929,107.226 81.566,93.248 C 83.58,82.589 57.867,86.86 58.791,93.913 L 58.791,93.913 z ";

// TODO: add render method? (it would replace the miniSvgRender function)
const MiniSvg = struct {
width: f64,
height: f64,
path: []const u8,
};

var gnome_foot_logo = MiniSvg{
.width = 96.2152,
.height = 118.26,
.path = path,
};

// TODO: miniSvgRender
fn miniSvgRender(shape: *MiniSvg, cr: ?cairo.CContext, do_path: c_int) void {
log.debug("miniSvgRender", .{});
if (do_path == 1) {
log.debug("do_path is TRUE", .{});
} else {
log.debug("do_path is FALSE", .{});
}
}

fn shapeRenderer(cr: ?cairo.CContext, attr: pc.PangoAttrShape, do_path: c_int, data: ?*c_void) callconv(.C) void {
log.debug("shapeRenderer", .{});
if (do_path == 1) {
log.debug("do_path is TRUE", .{});
} else {
log.debug("do_path is FALSE", .{});
}
// log.debug("attr {}", .{ attr });
// log.debug("PangoAttrShape {}", .{ attr.* });
log.debug("PangoAttrShape.data {}", .{attr.*.data});
// TODO: how to cast PangoAttrShape.data into *MiniSvg ? The alignment
// doesn't match.
// const shape = @ptrCast(*MiniSvg, attr.*.data.?);
// const shape = (MiniSvg *) attr.data; // @ptrCast a MiniSvg ?

log.debug("ink_rect.width {}", .{attr.*.ink_rect.width});
log.debug("ink_rect.height {}", .{attr.*.ink_rect.height});

// scale_x = (double) attr->ink_rect.width / (PANGO_SCALE * shape->width );
// scale_y = (double) attr->ink_rect.height / (PANGO_SCALE * shape->height);

// cr.relMoveTo((double) attr->ink_rect.x / PANGO_SCALE, (double) attr->ink_rect.y / PANGO_SCALE);
// cr.scale(scale_x, scale_y);
// miniSvgRender(shape, cr, do_path);
// this should probably be:
// miniSvg.render(cr, do_path);

// @panic("TODO: remove me when shapeRenderer is correct");
}

// TODO: how to return a ?*c_void type?
// fn pangoAttrDataCopyFunc(user_data: ?*const c_void) callconv(.C) ?*c_void {
// log.debug("pangoAttrDataCopyFunc", .{});
// log.debug("user_data {}", .{user_data});
// return @ptrCast(?*c_void, user_data);
// }
const pangoAttrDataCopyFunc: ?pc.PangoAttrDataCopyFunc = null;

fn gDestroyNotify(data: ?*c_void) callconv(.C) void {
log.debug("gDestroyNotify", .{});
// log.debug("data {}", .{data.?.*}); // data.? is opaque
}
// const gDestroyNotify: ?pc.GDestroyNotify = null;

fn getLayout(cr: *cairo.Context) !pc.Layout {
var ink_rect = try pc.Rectangle.new(1 * pc.SCALE, -11 * pc.SCALE, 8 * pc.SCALE, 10 * pc.SCALE);
var logical_rect = try pc.Rectangle.new(0 * pc.SCALE, -12 * pc.SCALE, 10 * pc.SCALE, 12 * pc.SCALE);

var layout = try pc.Layout.create(cr);

var ctx = try layout.getContext();
ctx.setShapeRenderer(shapeRenderer, null, null);
layout.setText(text);

var attrs = try pc.AttrList.new();
defer attrs.destroy();

var idx = std.mem.indexOf(u8, text[0..], BULLET);
while (idx != null) {
const str = text[idx.?..];
// log.debug("idx {} str.len {}", .{idx, str.len});
var attr = try pc.Attribute.newShapeWithData(MiniSvg, &ink_rect, &logical_rect, &gnome_foot_logo, pangoAttrDataCopyFunc, gDestroyNotify);
// TODO: move this ptrCast and intCast to pango.zig
// https://stackoverflow.com/questions/18659120/subtracting-two-strings-in-c
const str_addr = @intCast(c_uint, @ptrToInt(str.ptr));
const text_addr = @intCast(c_uint, @ptrToInt(text));
attr.c_ptr.*.start_index = str_addr - text_addr;
attr.c_ptr.*.end_index = attr.c_ptr.*.start_index + @intCast(c_uint, BULLET.len);
attrs.insert(&attr);

// find index for next iteration
const i_rel = std.mem.indexOf(u8, text[idx.? + BULLET.len ..], BULLET);
if (i_rel == null) {
idx = null;
} else {
idx = idx.? + i_rel.? + 1;
}
}

layout.setAttributes(&attrs);
return layout;
}

fn drawText(cr: *cairo.Context, width: ?f64, height: ?f64) !pc.Size {
log.info("=== drawText ===", .{});
var layout = try getLayout(cr);
defer layout.destroy();

var size = pc.Size{ .width = 0.0, .height = 0.0 };
const margin = 10.0;

if ((width != null) or (height != null)) {
const original_size = layout.getPixelSize();
if (width != null) {
size.width = original_size.width + 2.0 * margin;
}
if (height != null) {
size.height = original_size.height + 2.0 * margin;
}
}

cr.moveTo(margin, margin);
layout.show(cr);

return size;
}

pub fn main() !void {
// First create and use a 0x0 surface, to measure how large the final
// surface needs to be.
var surface = try cairo.Surface.image(0.0, 0.0);
defer surface.destroy();

var cr = try cairo.Context.create(&surface);
defer cr.destroy();

const size = try drawText(&cr, null, null);

// TODO: Now create the final surface and draw to it. Reuse surface and cr?
var surface2 = try cairo.Surface.image(@floatToInt(u16, size.width), @floatToInt(u16, size.height));
defer surface2.destroy();

var cr2 = try cairo.Context.create(&surface);
defer cr2.destroy();

cr2.setSourceRgb(1.0, 1.0, 1.0); // white
cr2.paint();

cr2.setSourceRgb(0.0, 0.0, 0.5);
const size2 = try drawText(&cr2, size.width, size.height);

_ = surface2.writeToPng("examples/generated/pango_shape.png");
}
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