Set pango language through ctx.lang (#2526)

Co-authored-by: Caleb Hearon <caleb@chearon.net>

Author: mapmeld

CHANGELOG.md

@@ -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

index.d.ts

@@ -291,6 +291,7 @@ export class CanvasRenderingContext2D {
 	textAlign: CanvasTextAlign;
 	canvas: Canvas;
 	direction: 'ltr' | 'rtl';
+	lang: string;
 }
 
 export class CanvasGradient {

src/CanvasRenderingContext2d.cc

@@ -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();
@@ -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);
@@ -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);
+}
+
+/*
+ * 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.
  *
@@ -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;
@@ -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

src/CanvasRenderingContext2d.h

@@ -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");
@@ -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() {
@@ -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);
@@ -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);

test/canvas.test.js

@@ -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) {