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Replace dllimports in CairoCanvas #17

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lytico wants to merge 3 commits into from
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Replace dllimports in CairoCanvas #17

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9148255
Replace P/Invoke-based gradients with `Cairo` gradients.
lytico Apr 1, 2026
8078b33
Replace P/Invoke-based surface dimension functions with native proper…
lytico Apr 1, 2026
a26db26
Replace P/Invoke-based text attributes with native Pango functions.
lytico Apr 1, 2026
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113 changes: 34 additions & 79 deletions src/Platform.Maui.Linux.Gtk4/Graphics/CairoCanvas.cs
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Original file line number Diff line number Diff line change
@@ -1,8 +1,15 @@
using System.Numerics;
using System.Runtime.InteropServices;
using Cairo;
using Microsoft.Maui.Graphics;
using Microsoft.Maui.Graphics.Text;
using Pango;
using Attribute = Pango.Attribute;
using Color = Microsoft.Maui.Graphics.Color;
using IImage = Microsoft.Maui.Graphics.IImage;
using LineCap = Microsoft.Maui.Graphics.LineCap;
using LineJoin = Microsoft.Maui.Graphics.LineJoin;
using Style = Pango.Style;

namespace Platform.Maui.Linux.Gtk4.Graphics;

Expand Down Expand Up @@ -217,9 +224,9 @@ public void DrawText(IAttributedText value, float x, float y, float width, float

// Apply text attributes (bold, italic, color, etc.)
var attrList = BuildPangoAttrList(value);
if (attrList != IntPtr.Zero)
if (attrList != null)
{
pango_layout_set_attributes(layout.Handle.DangerousGetHandle(), attrList);
layout.SetAttributes ( attrList );
// attrList ownership transfers to layout
}

Expand Down Expand Up @@ -303,8 +310,8 @@ public void DrawImage(IImage image, float x, float y, float width, float height)

_cr.Save();

double scaleX = width / cairo_image_surface_get_width(surface.Handle.DangerousGetHandle());
double scaleY = height / cairo_image_surface_get_height(surface.Handle.DangerousGetHandle());
double scaleX = width / surface.Width;
double scaleY = height / surface.Height;
_cr.Translate(x, y);
_cr.Scale(scaleX, scaleY);

Expand Down Expand Up @@ -495,15 +502,15 @@ private void ApplyLinearGradient(LinearGradientPaint paint, RectF rect)
double x1 = rect.X + paint.EndPoint.X * rect.Width;
double y1 = rect.Y + paint.EndPoint.Y * rect.Height;

var patternHandle = cairo_pattern_create_linear(x0, y0, x1, y1);
var gradient = new LinearGradient (x0, y0, x1, y1);
try
{
AddGradientStops(patternHandle, paint.GradientStops);
cairo_set_source(_cr.Handle.DangerousGetHandle(), patternHandle);
AddGradientStops(gradient, paint.GradientStops);
_cr.SetSource ( gradient);
}
finally
{
cairo_pattern_destroy(patternHandle);
gradient.Dispose ();
}
}

Expand All @@ -513,26 +520,26 @@ private void ApplyRadialGradient(RadialGradientPaint paint, RectF rect)
double cy = rect.Y + paint.Center.Y * rect.Height;
double radius = Math.Max(rect.Width, rect.Height) * paint.Radius;

var patternHandle = cairo_pattern_create_radial(cx, cy, 0, cx, cy, radius);
var gradient = new RadialGradient(cx, cy, 0, cx, cy, radius);
try
{
AddGradientStops(patternHandle, paint.GradientStops);
cairo_set_source(_cr.Handle.DangerousGetHandle(), patternHandle);
AddGradientStops(gradient, paint.GradientStops);
_cr.SetSource(gradient);
}
finally
{
cairo_pattern_destroy(patternHandle);
gradient.Dispose();
}
}

private void AddGradientStops(nint pattern, PaintGradientStop[]? stops)
private void AddGradientStops(Gradient pattern, PaintGradientStop[]? stops)
{
if (stops == null) return;

foreach (var stop in stops)
{
var color = stop.Color;
cairo_pattern_add_color_stop_rgba(pattern, stop.Offset,
pattern.AddColorStopRgba ( stop.Offset,
color.Red, color.Green, color.Blue, color.Alpha * _alpha);
}
}
Expand Down Expand Up @@ -576,12 +583,12 @@ private Pango.Layout CreatePangoLayout(string text, IFont? font = null, float? f
/// Builds a PangoAttrList from IAttributedText runs.
/// Returns IntPtr.Zero if no attributes to apply.
/// </summary>
private static IntPtr BuildPangoAttrList(IAttributedText attributedText)
private static AttrList? BuildPangoAttrList(IAttributedText attributedText)
{
if (attributedText.Runs == null || attributedText.Runs.Count == 0)
return IntPtr.Zero;
return default;

var attrList = pango_attr_list_new();
var attrList = Pango.AttrList.New ();
var text = attributedText.Text;

foreach (var run in attributedText.Runs)
Expand All @@ -594,21 +601,21 @@ private static IntPtr BuildPangoAttrList(IAttributedText attributedText)
if (attrs == null) continue;

if (attrs.ContainsKey(TextAttribute.Bold))
InsertPangoAttr(attrList, pango_attr_weight_new(700), byteStart, byteEnd);
InsertPangoAttr(attrList, Pango.Functions.AttrWeightNew (Pango.Weight.Bold));

if (attrs.ContainsKey(TextAttribute.Italic))
InsertPangoAttr(attrList, pango_attr_style_new(2), byteStart, byteEnd);
InsertPangoAttr(attrList, Pango.Functions.AttrStyleNew (Style.Italic));

if (attrs.ContainsKey(TextAttribute.Underline))
InsertPangoAttr(attrList, pango_attr_underline_new(1), byteStart, byteEnd);
InsertPangoAttr(attrList, Pango.Functions.AttrUnderlineNew (Underline.Single));

if (attrs.ContainsKey(TextAttribute.Strikethrough))
InsertPangoAttr(attrList, pango_attr_strikethrough_new(true), byteStart, byteEnd);
InsertPangoAttr(attrList, Pango.Functions.AttrStrikethroughNew (true));

if (attrs.TryGetValue(TextAttribute.FontSize, out var fontSizeStr)
&& float.TryParse(fontSizeStr, out float attrFontSize))
{
InsertPangoAttr(attrList, pango_attr_size_new((int)(attrFontSize * Pango.Constants.SCALE)), byteStart, byteEnd);
InsertPangoAttr(attrList, Pango.Functions.AttrSizeNew ((int)(attrFontSize * Pango.Constants.SCALE)));
}

if (attrs.TryGetValue(TextAttribute.Color, out var colorStr))
Expand All @@ -618,7 +625,7 @@ private static IntPtr BuildPangoAttrList(IAttributedText attributedText)
ushort r = (ushort)(color.Red * 65535);
ushort g = (ushort)(color.Green * 65535);
ushort b = (ushort)(color.Blue * 65535);
InsertPangoAttr(attrList, pango_attr_foreground_new(r, g, b), byteStart, byteEnd);
InsertPangoAttr(attrList, Pango.Functions.AttrForegroundNew (r, g, b));
}
}
}
Expand All @@ -630,12 +637,11 @@ private static IntPtr BuildPangoAttrList(IAttributedText attributedText)
/// Sets start/end byte indices on a PangoAttribute and inserts it into the list.
/// PangoAttribute struct layout: klass (ptr), start_index (uint), end_index (uint)
/// </summary>
private static void InsertPangoAttr(IntPtr attrList, IntPtr attr, int byteStart, int byteEnd)
private static void InsertPangoAttr (AttrList attrList, Attribute attr)
{
if (attr == IntPtr.Zero) return;
Marshal.WriteInt32(attr, IntPtr.Size, byteStart);
Marshal.WriteInt32(attr, IntPtr.Size + 4, byteEnd);
pango_attr_list_insert(attrList, attr);
if (attr is null) return;

attrList.Insert (attr);
}

private void ApplyOperator()
Expand Down Expand Up @@ -753,55 +759,4 @@ private void DrawPathInternal(PathF path)
}
}

// --- Cairo P/Invoke for gradient patterns ---

[DllImport("libcairo.so.2")]
private static extern nint cairo_pattern_create_linear(double x0, double y0, double x1, double y1);

[DllImport("libcairo.so.2")]
private static extern nint cairo_pattern_create_radial(double cx0, double cy0, double radius0, double cx1, double cy1, double radius1);

[DllImport("libcairo.so.2")]
private static extern void cairo_pattern_add_color_stop_rgba(nint pattern, double offset, double red, double green, double blue, double alpha);

[DllImport("libcairo.so.2")]
private static extern void cairo_pattern_destroy(nint pattern);

[DllImport("libcairo.so.2")]
private static extern void cairo_set_source(nint cr, nint pattern);

[DllImport("libcairo.so.2")]
private static extern int cairo_image_surface_get_width(nint surface);

[DllImport("libcairo.so.2")]
private static extern int cairo_image_surface_get_height(nint surface);

// --- Pango P/Invoke for attributed text ---

[DllImport("libpango-1.0.so.0")]
private static extern IntPtr pango_attr_list_new();

[DllImport("libpango-1.0.so.0")]
private static extern void pango_attr_list_insert(IntPtr list, IntPtr attr);

[DllImport("libpango-1.0.so.0")]
private static extern void pango_layout_set_attributes(IntPtr layout, IntPtr attrs);

[DllImport("libpango-1.0.so.0")]
private static extern IntPtr pango_attr_weight_new(int weight);

[DllImport("libpango-1.0.so.0")]
private static extern IntPtr pango_attr_style_new(int style);

[DllImport("libpango-1.0.so.0")]
private static extern IntPtr pango_attr_underline_new(int underline);

[DllImport("libpango-1.0.so.0")]
private static extern IntPtr pango_attr_strikethrough_new(bool strikethrough);

[DllImport("libpango-1.0.so.0")]
private static extern IntPtr pango_attr_size_new(int size);

[DllImport("libpango-1.0.so.0")]
private static extern IntPtr pango_attr_foreground_new(ushort red, ushort green, ushort blue);
}