cairo_text_extents_t 未被 lua 识别

Question

我正在 lua 中编写一些小部件，供 conky 使用以显示一些内容。我达到了我想要居中文本的程度。按照 this 教程，我将 C 代码移植到 lua 代码中，所以它现在看起来像这样：

local extents
local utf8 = "cairo"
local x, y
cairo_select_font_face(cr, "Ubuntu", CAIRO_FONT_SLANT_NORMAL, CAIRO_FONT_WEIGHT_NORMAL)
cairo_set_font_size(cr, 13)
cairo_text_extents(cr, utf8, extents)
x = 128.0 - (extents.width / 2 + extents.x_bearing)
y = 128.0 - (extents.height / 2 + extents.y_bearing)

cairo_move_to(cr, x, y)
cairo_show_text(cr, utf8)

我现在处理的问题是 C 数据类型 cairo_text_extents_t 应该传递给 cairo_text_extents 不被 lua 识别，事实上conky 关闭，没有任何输出。

有没有办法让 lua 识别该数据类型？

Answer 1

我终于找到了答案。在 conky 中，存在一个函数可以满足我的需求，如指定的那样 here:

cairo_text_extents_t:create() function
Call this function to return a new cairo_text_extents_t structure. A creation function for this structure is not provided by the cairo API. After calling this, you should use tolua.takeownership() on the return value to ensure ownership is passed properly.

因此，执行以下操作就足够了：

local extents = cairo_text_extents_t:create()
tolua.takeownership(extents)
local utf8 = "cairo"
local x, y
cairo_select_font_face(cr, "Ubuntu", CAIRO_FONT_SLANT_NORMAL, CAIRO_FONT_WEIGHT_NORMAL)
cairo_set_font_size(cr, 52)
cairo_text_extents(cr, utf8, extents)
x = 128.0 - (extents.width / 2 + extents.x_bearing)
y = 128.0 - (extents.height / 2 + extents.y_bearing)

cairo_move_to (cr, x, y)
cairo_show_text (cr, utf8)

cairo_text_extents_t 未被 lua 识别

cairo_text_extents_t is not recognized by lua

lua

cairo

conky