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Set pango language through ctx.lang #2526

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Merged
merged 5 commits into from
Aug 17, 2025
Merged

Set pango language through ctx.lang #2526

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0d3abd3
attempt to show differences by ctx.lang
mapmeld Aug 2, 2025
9a0d513
use pango_context_get_language instead of stored lang state
mapmeld Aug 4, 2025
dc7eac9
Revert "use pango_context_get_language instead of stored lang state"
mapmeld Aug 17, 2025
b5fcf9b
Remove extra pango_cairo_update_layout
mapmeld Aug 17, 2025
f865df7
store language in state->lang until needed
mapmeld Aug 17, 2025
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1 change: 1 addition & 0 deletions CHANGELOG.md
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Expand Up @@ -9,6 +9,7 @@ project adheres to [Semantic Versioning](http://semver.org/).
==================
### Changed
### Added
* Added `ctx.lang` to set the ISO language code for text
### Fixed

3.1.2
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1 change: 1 addition & 0 deletions index.d.ts
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Expand Up @@ -291,6 +291,7 @@ export class CanvasRenderingContext2D {
textAlign: CanvasTextAlign;
canvas: Canvas;
direction: 'ltr' | 'rtl';
lang: string;
}

export class CanvasGradient {
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30 changes: 28 additions & 2 deletions src/CanvasRenderingContext2d.cc
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Expand Up @@ -43,7 +43,7 @@ constexpr double twoPi = M_PI * 2.;
#define PANGO_LAYOUT_GET_METRICS(LAYOUT) pango_context_get_metrics( \
pango_layout_get_context(LAYOUT), \
pango_layout_get_font_description(LAYOUT), \
pango_context_get_language(pango_layout_get_context(LAYOUT)))
pango_language_from_string(state->lang.c_str()))

inline static bool checkArgs(const Napi::CallbackInfo&info, double *args, int argsNum, int offset = 0){
Napi::Env env = info.Env();
Expand Down Expand Up @@ -162,7 +162,8 @@ Context2d::Initialize(Napi::Env& env, Napi::Object& exports) {
InstanceAccessor<&Context2d::GetFont, &Context2d::SetFont>("font", napi_default_jsproperty),
InstanceAccessor<&Context2d::GetTextBaseline, &Context2d::SetTextBaseline>("textBaseline", napi_default_jsproperty),
InstanceAccessor<&Context2d::GetTextAlign, &Context2d::SetTextAlign>("textAlign", napi_default_jsproperty),
InstanceAccessor<&Context2d::GetDirection, &Context2d::SetDirection>("direction", napi_default_jsproperty)
InstanceAccessor<&Context2d::GetDirection, &Context2d::SetDirection>("direction", napi_default_jsproperty),
InstanceAccessor<&Context2d::GetLanguage, &Context2d::SetLanguage>("lang", napi_default_jsproperty)
});

exports.Set("CanvasRenderingContext2d", ctor);
Expand Down Expand Up @@ -786,6 +787,25 @@ Context2d::SetDirection(const Napi::CallbackInfo& info, const Napi::Value& value
state->direction = dir;
}

/*
* Get language.
*/
Napi::Value
Context2d::GetLanguage(const Napi::CallbackInfo& info) {
return Napi::String::New(env, state->lang);
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Should this call pango_context_get_language() for consistency with PANGO_LAYOUT_GET_METRICS? This would avoid the need to maintain lang as parallel state in canvas_state_t.

node-canvas/src/CanvasRenderingContext2d.cc

Line 46 in 0d3abd3

pango_context_get_language(pango_layout_get_context(LAYOUT)))

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makes sense, done ✅

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With the second commit, I don't think ctx.save() and ctx.restore() will update ctx.lang, will it? It needs to be on the canvas_state_t.

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In that case, should PANGO_LAYOUT_GET_METRICS use the lang field instead of pango_context_get_language()?

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The layout should be up-to-date there, but good call looking at that. I'll start a review with my thoughts...

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maybe the better way to get the language before it is lazily committed?

if (state->lang == "") { // unchanged
  pango_context_get_language()
} else {
  pango_language_from_string(state->lang)
}

}

/*
* Set language.
*/
void
Context2d::SetLanguage(const Napi::CallbackInfo& info, const Napi::Value& value) {
if (!value.IsString()) return;

std::string lang = value.As<Napi::String>();
state->lang = lang;
}

/*
* Put image data.
*
Expand Down Expand Up @@ -2490,6 +2510,9 @@ Context2d::paintText(const Napi::CallbackInfo& info, bool stroke) {

checkFonts();
pango_layout_set_text(layout, str.c_str(), -1);
if (state->lang != "") {
pango_context_set_language(pango_layout_get_context(_layout), pango_language_from_string(state->lang.c_str()));
}
pango_cairo_update_layout(context(), layout);

PangoDirection pango_dir = state->direction == "ltr" ? PANGO_DIRECTION_LTR : PANGO_DIRECTION_RTL;
Expand Down Expand Up @@ -2802,6 +2825,9 @@ Context2d::MeasureText(const Napi::CallbackInfo& info) {

checkFonts();
pango_layout_set_text(layout, str.Utf8Value().c_str(), -1);
if (state->lang != "") {
pango_context_set_language(pango_layout_get_context(_layout), pango_language_from_string(state->lang.c_str()));
}
pango_cairo_update_layout(ctx, layout);

// Normally you could use pango_layout_get_pixel_extents and be done, or use
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4 changes: 4 additions & 0 deletions src/CanvasRenderingContext2d.h
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Expand Up @@ -36,6 +36,7 @@ struct canvas_state_t {
canvas_draw_mode_t textDrawingMode = TEXT_DRAW_PATHS;
bool imageSmoothingEnabled = true;
std::string direction = "ltr";
std::string lang = "";

canvas_state_t() {
fontDescription = pango_font_description_from_string("sans");
Expand All @@ -61,6 +62,7 @@ struct canvas_state_t {
fontDescription = pango_font_description_copy(other.fontDescription);
font = other.font;
imageSmoothingEnabled = other.imageSmoothingEnabled;
lang = other.lang;
}

~canvas_state_t() {
Expand Down Expand Up @@ -157,6 +159,7 @@ class Context2d : public Napi::ObjectWrap<Context2d> {
Napi::Value GetFont(const Napi::CallbackInfo& info);
Napi::Value GetTextBaseline(const Napi::CallbackInfo& info);
Napi::Value GetTextAlign(const Napi::CallbackInfo& info);
Napi::Value GetLanguage(const Napi::CallbackInfo& info);
void SetPatternQuality(const Napi::CallbackInfo& info, const Napi::Value& value);
void SetImageSmoothingEnabled(const Napi::CallbackInfo& info, const Napi::Value& value);
void SetGlobalCompositeOperation(const Napi::CallbackInfo& info, const Napi::Value& value);
Expand All @@ -179,6 +182,7 @@ class Context2d : public Napi::ObjectWrap<Context2d> {
void SetFont(const Napi::CallbackInfo& info, const Napi::Value& value);
void SetTextBaseline(const Napi::CallbackInfo& info, const Napi::Value& value);
void SetTextAlign(const Napi::CallbackInfo& info, const Napi::Value& value);
void SetLanguage(const Napi::CallbackInfo& info, const Napi::Value& value);
#if CAIRO_VERSION >= CAIRO_VERSION_ENCODE(1, 16, 0)
void BeginTag(const Napi::CallbackInfo& info);
void EndTag(const Napi::CallbackInfo& info);
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3 changes: 2 additions & 1 deletion test/canvas.test.js
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Expand Up @@ -2490,7 +2490,8 @@ describe('Canvas', function () {
['patternQuality', 'best'],
// ['quality', 'best'], // doesn't do anything, TODO remove
['textDrawingMode', 'glyph'],
['antialias', 'gray']
['antialias', 'gray'],
['lang', 'eu']
]

for (const [k, v] of state) {
Expand Down