开罗:把整个画作为一种模式 [英] Cairo: grabbing the whole drawing as a pattern
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问题描述
我可能缺少关于 cairo
的概念。我使用以下帮助类绘制:
I am probably missing something conceptual about cairo
. I draw using the following helper class:
struct GroupLock {
GroupLock(Graphics &g) : g_(g) {
cairo_push_group(g_.cr);
}
~GroupLock() {
cairo_pop_group_to_source(g_.cr);
cairo_paint(g_.cr);
cairo_surface_flush(g_.surface);
XFlush(g_.display);
}
private:
Graphics &g_;
};
我的所有绘图函数都是以下形式:
All my drawing functions are of the form:
void drawSomething(Graphics &g) {
GroupLock lock{g}; (void)lock;
... // some drawing
}
绘图函数设置源(通过使用 GroupLock
),并使之前的源无法访问。如何修改此代码以并置源?我希望能够通过执行以下操作来抓取整个绘图:
Each call to such a drawing function sets the source (by virtue of using GroupLock
) and makes the previous source unreachable. How can I modify this code to "concatenate" the sources instead? I would like be able to grab the whole drawing as a pattern by doing:
cairo_pattern_t *p_ = cairo_get_source(g_.cr);
cairo_pattern_reference(p_);
推荐答案
经过几个小时的努力后,所有需要做的是修改构造函数读取这样:
After struggling for hours, here it is! All that needed to be done is to modify the constructor to read like this:
p_ = cairo_get_source(g_.cr);
cairo_pattern_reference(p_);
cairo_push_group(g_.cr);
cairo_set_source (g_.cr, p_);
cairo_paint(g_.cr);
cairo_pattern_destroy(p_);
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