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remove save() limit, improve save/restore perf, fix some props
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1. One WPT test fails if there are not at least 512 save/restore slots. This removes that limit entirely.

2. Gets rid of clunky C code and uses `std::stack` with a proper C++ class. End result is >1.6x faster with MSVC.

3. Reorders fields and types some enums so the state struct shrinks from 192 bytes to 168 bytes (-24 bytes; i.e. 24 bytes saved per state).

4. Fixes several properties that were not saved/restored: `textBaseline`, `textAlign`. `quality` is not saved/restored, but it's not wired up to anything and needs to be removed.

Fixes #1936
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@zbjornson
zbjornson committed Oct 22, 2022
1 parent b3e7df3 commit 0e6504a
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Showing 7 changed files with 200 additions and 141 deletions.
3 changes: 3 additions & 0 deletions CHANGELOG.md
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Expand Up @@ -8,8 +8,11 @@ project adheres to [Semantic Versioning](http://semver.org/).
(Unreleased)
==================
### Changed
* Improve performance and memory usage of `save()`/`restore()`.
* `save()`/`restore()` no longer have a maximum depth (previously 64 states).
### Added
### Fixed
* `textBaseline` and `textAlign` were not saved/restored by `save()`/`restore()`. ([#1936](https://github.com/Automattic/node-canvas/issues/2029))

2.10.1
==================
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2 changes: 1 addition & 1 deletion Readme.md
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Expand Up @@ -91,7 +91,7 @@ This project is an implementation of the Web Canvas API and implements that API
* [CanvasRenderingContext2D#patternQuality](#canvasrenderingcontext2dpatternquality)
* [CanvasRenderingContext2D#quality](#canvasrenderingcontext2dquality)
* [CanvasRenderingContext2D#textDrawingMode](#canvasrenderingcontext2dtextdrawingmode)
* [CanvasRenderingContext2D#globalCompositeOperator = 'saturate'](#canvasrenderingcontext2dglobalcompositeoperator--saturate)
* [CanvasRenderingContext2D#globalCompositeOperation = 'saturate'](#canvasrenderingcontext2dglobalcompositeoperation--saturate)
* [CanvasRenderingContext2D#antialias](#canvasrenderingcontext2dantialias)

### createCanvas()
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12 changes: 12 additions & 0 deletions benchmarks/run.js
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Expand Up @@ -64,6 +64,18 @@ function done (benchmark, times, start, isAsync) {

// node-canvas

bm('save/restore', function () {
for (let i = 0; i < 1000; i++) {
const max = i & 15
for (let j = 0; j < max; ++j) {
ctx.save()
}
for (let j = 0; j < max; ++j) {
ctx.restore()
}
}
})

bm('fillStyle= name', function () {
for (let i = 0; i < 10000; i++) {
ctx.fillStyle = '#fefefe'
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32 changes: 23 additions & 9 deletions src/Canvas.h
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Expand Up @@ -11,15 +11,6 @@
#include <vector>
#include <cstddef>

/*
* Maxmimum states per context.
* TODO: remove/resize
*/

#ifndef CANVAS_MAX_STATES
#define CANVAS_MAX_STATES 64
#endif

/*
* FontFace describes a font file in terms of one PangoFontDescription that
* will resolve to it and one that the user describes it as (like @font-face)
Expand All @@ -31,6 +22,29 @@ class FontFace {
unsigned char file_path[1024];
};

enum text_baseline_t : uint8_t {
TEXT_BASELINE_ALPHABETIC = 0,
TEXT_BASELINE_TOP = 1,
TEXT_BASELINE_BOTTOM = 2,
TEXT_BASELINE_MIDDLE = 3,
TEXT_BASELINE_IDEOGRAPHIC = 4,
TEXT_BASELINE_HANGING = 5
};

enum text_align_t : int8_t {
TEXT_ALIGNMENT_LEFT = -1,
TEXT_ALIGNMENT_CENTER = 0,
TEXT_ALIGNMENT_RIGHT = 1,
// Currently same as LEFT and RIGHT without RTL support:
TEXT_ALIGNMENT_START = -2,
TEXT_ALIGNMENT_END = 2
};

enum canvas_draw_mode_t : uint8_t {
TEXT_DRAW_PATHS,
TEXT_DRAW_GLYPHS
};

/*
* Canvas.
*/
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155 changes: 56 additions & 99 deletions src/CanvasRenderingContext2d.cc
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Expand Up @@ -38,19 +38,6 @@ Nan::Persistent<FunctionTemplate> Context2d::constructor;

constexpr double twoPi = M_PI * 2.;

/*
* Text baselines.
*/

enum {
TEXT_BASELINE_ALPHABETIC
, TEXT_BASELINE_TOP
, TEXT_BASELINE_BOTTOM
, TEXT_BASELINE_MIDDLE
, TEXT_BASELINE_IDEOGRAPHIC
, TEXT_BASELINE_HANGING
};

/*
* Simple helper macro for a rather verbose function call.
*/
Expand Down Expand Up @@ -178,20 +165,16 @@ Context2d::Context2d(Canvas *canvas) {
_canvas = canvas;
_context = canvas->createCairoContext();
_layout = pango_cairo_create_layout(_context);
state = states[stateno = 0] = (canvas_state_t *) malloc(sizeof(canvas_state_t));

resetState(true);
states.emplace();
state = &states.top();
pango_layout_set_font_description(_layout, state->fontDescription);
}

/*
* Destroy cairo context.
*/

Context2d::~Context2d() {
while(stateno >= 0) {
pango_font_description_free(states[stateno]->fontDescription);
free(states[stateno--]);
}
g_object_unref(_layout);
cairo_destroy(_context);
_resetPersistentHandles();
Expand All @@ -201,41 +184,17 @@ Context2d::~Context2d() {
* Reset canvas state.
*/

void Context2d::resetState(bool init) {
if (!init) {
pango_font_description_free(state->fontDescription);
}

state->shadowBlur = 0;
state->shadowOffsetX = state->shadowOffsetY = 0;
state->globalAlpha = 1;
state->textAlignment = -1;
state->fillPattern = nullptr;
state->strokePattern = nullptr;
state->fillGradient = nullptr;
state->strokeGradient = nullptr;
state->textBaseline = TEXT_BASELINE_ALPHABETIC;
rgba_t transparent = { 0, 0, 0, 1 };
rgba_t transparent_black = { 0, 0, 0, 0 };
state->fill = transparent;
state->stroke = transparent;
state->shadow = transparent_black;
state->patternQuality = CAIRO_FILTER_GOOD;
state->imageSmoothingEnabled = true;
state->textDrawingMode = TEXT_DRAW_PATHS;
state->fontDescription = pango_font_description_from_string("sans");
pango_font_description_set_absolute_size(state->fontDescription, 10 * PANGO_SCALE);
void Context2d::resetState() {
states.pop();
states.emplace();
pango_layout_set_font_description(_layout, state->fontDescription);

_resetPersistentHandles();
}

void Context2d::_resetPersistentHandles() {
_fillStyle.Reset();
_strokeStyle.Reset();
_font.Reset();
_textBaseline.Reset();
_textAlign.Reset();
}

/*
Expand All @@ -244,13 +203,9 @@ void Context2d::_resetPersistentHandles() {

void
Context2d::save() {
if (stateno < CANVAS_MAX_STATES) {
cairo_save(_context);
states[++stateno] = (canvas_state_t *) malloc(sizeof(canvas_state_t));
memcpy(states[stateno], state, sizeof(canvas_state_t));
states[stateno]->fontDescription = pango_font_description_copy(states[stateno-1]->fontDescription);
state = states[stateno];
}
cairo_save(_context);
states.emplace(states.top());
state = &states.top();
}

/*
Expand All @@ -259,12 +214,10 @@ Context2d::save() {

void
Context2d::restore() {
if (stateno > 0) {
if (states.size() > 1) {
cairo_restore(_context);
pango_font_description_free(states[stateno]->fontDescription);
free(states[stateno]);
states[stateno] = NULL;
state = states[--stateno];
states.pop();
state = &states.top();
pango_layout_set_font_description(_layout, state->fontDescription);
}
}
Expand Down Expand Up @@ -2496,13 +2449,12 @@ Context2d::setTextPath(double x, double y) {
PangoRectangle logical_rect;

switch (state->textAlignment) {
// center
case 0:
case TEXT_ALIGNMENT_CENTER:
pango_layout_get_pixel_extents(_layout, NULL, &logical_rect);
x -= logical_rect.width / 2;
break;
// right
case 1:
case TEXT_ALIGNMENT_END:
case TEXT_ALIGNMENT_RIGHT:
pango_layout_get_pixel_extents(_layout, NULL, &logical_rect);
x -= logical_rect.width;
break;
Expand Down Expand Up @@ -2629,15 +2581,17 @@ NAN_SETTER(Context2d::SetFont) {

NAN_GETTER(Context2d::GetTextBaseline) {
Context2d *context = Nan::ObjectWrap::Unwrap<Context2d>(info.This());
Isolate *iso = Isolate::GetCurrent();
Local<Value> font;

if (context->_textBaseline.IsEmpty())
font = Nan::New("alphabetic").ToLocalChecked();
else
font = context->_textBaseline.Get(iso);

info.GetReturnValue().Set(font);
const char* baseline;
switch (context->state->textBaseline) {
default:
case TEXT_BASELINE_ALPHABETIC: baseline = "alphabetic"; break;
case TEXT_BASELINE_TOP: baseline = "top"; break;
case TEXT_BASELINE_BOTTOM: baseline = "bottom"; break;
case TEXT_BASELINE_MIDDLE: baseline = "middle"; break;
case TEXT_BASELINE_IDEOGRAPHIC: baseline = "ideographic"; break;
case TEXT_BASELINE_HANGING: baseline = "hanging"; break;
}
info.GetReturnValue().Set(Nan::New(baseline).ToLocalChecked());
}

/*
Expand All @@ -2648,20 +2602,19 @@ NAN_SETTER(Context2d::SetTextBaseline) {
if (!value->IsString()) return;

Nan::Utf8String opStr(Nan::To<String>(value).ToLocalChecked());
const std::map<std::string, int32_t> modes = {
{"alphabetic", 0},
{"top", 1},
{"bottom", 2},
{"middle", 3},
{"ideographic", 4},
{"hanging", 5}
const std::map<std::string, text_baseline_t> modes = {
{"alphabetic", TEXT_BASELINE_ALPHABETIC},
{"top", TEXT_BASELINE_TOP},
{"bottom", TEXT_BASELINE_BOTTOM},
{"middle", TEXT_BASELINE_MIDDLE},
{"ideographic", TEXT_BASELINE_IDEOGRAPHIC},
{"hanging", TEXT_BASELINE_HANGING}
};
auto op = modes.find(*opStr);
if (op == modes.end()) return;

Context2d *context = Nan::ObjectWrap::Unwrap<Context2d>(info.This());
context->state->textBaseline = op->second;
context->_textBaseline.Reset(value);
}

/*
Expand All @@ -2670,15 +2623,17 @@ NAN_SETTER(Context2d::SetTextBaseline) {

NAN_GETTER(Context2d::GetTextAlign) {
Context2d *context = Nan::ObjectWrap::Unwrap<Context2d>(info.This());
Isolate *iso = Isolate::GetCurrent();
Local<Value> font;

if (context->_textAlign.IsEmpty())
font = Nan::New("start").ToLocalChecked();
else
font = context->_textAlign.Get(iso);

info.GetReturnValue().Set(font);
const char* align;
switch (context->state->textAlignment) {
default:
// TODO the default is supposed to be "start"
case TEXT_ALIGNMENT_LEFT: align = "left"; break;
case TEXT_ALIGNMENT_START: align = "start"; break;
case TEXT_ALIGNMENT_CENTER: align = "center"; break;
case TEXT_ALIGNMENT_RIGHT: align = "right"; break;
case TEXT_ALIGNMENT_END: align = "end"; break;
}
info.GetReturnValue().Set(Nan::New(align).ToLocalChecked());
}

/*
Expand All @@ -2689,19 +2644,18 @@ NAN_SETTER(Context2d::SetTextAlign) {
if (!value->IsString()) return;

Nan::Utf8String opStr(Nan::To<String>(value).ToLocalChecked());
const std::map<std::string, int32_t> modes = {
{"center", 0},
{"left", -1},
{"start", -1},
{"right", 1},
{"end", 1}
const std::map<std::string, text_align_t> modes = {
{"center", TEXT_ALIGNMENT_CENTER},
{"left", TEXT_ALIGNMENT_LEFT},
{"start", TEXT_ALIGNMENT_START},
{"right", TEXT_ALIGNMENT_RIGHT},
{"end", TEXT_ALIGNMENT_END}
};
auto op = modes.find(*opStr);
if (op == modes.end()) return;

Context2d *context = Nan::ObjectWrap::Unwrap<Context2d>(info.This());
context->state->textAlignment = op->second;
context->_textAlign.Reset(value);
}

/*
Expand Down Expand Up @@ -2747,13 +2701,16 @@ NAN_METHOD(Context2d::MeasureText) {

double x_offset;
switch (context->state->textAlignment) {
case 0: // center
case TEXT_ALIGNMENT_CENTER:
x_offset = logical_rect.width / 2.;
break;
case 1: // right
case TEXT_ALIGNMENT_END:
case TEXT_ALIGNMENT_RIGHT:
x_offset = logical_rect.width;
break;
default: // left
case TEXT_ALIGNMENT_START:
case TEXT_ALIGNMENT_LEFT:
default:
x_offset = 0.0;
}

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