Merge pull request #51 from lite-xl/fontconfig

add fontconfig plugin

2 files changed, 92 insertions, 0 deletions

diff --git a/README.md b/README.md
index d43149b..5fac4d3 100644
--- a/README.md
+++ b/README.md
@@ -35,6 +35,7 @@ Plugin | Description
 [`exec`](plugins/exec.lua?raw=1) | Runs selected text through shell command and replaces with result
 [`ephemeraldocviews`](plugins/ephemeraldocviews.lua?raw=1) | Preview tabs. Opening a doc will replace the contents of the preview tab. Marks tabs as non-preview on any change.
 [`fallbackfonts`](https://github.com/takase1121/lite-fallback-fonts)* | Adds support for fallback fonts *([gif](https://raw.githubusercontent.com/takase1121/lite-fallback-fonts/master/assets/Iw18fI57J0.gif))*
+[`fontconfig`](plugins/fontconfig.lua?raw=1) | Allows users to load fonts with [fontconfig](https://www.freedesktop.org/software/fontconfig/fontconfig-user.html).
 [`formatter`](https://github.com/vincens2005/lite-formatters)* | formatters for various languages
 [`ghmarkdown`](plugins/ghmarkdown.lua?raw=1) | Opens a preview of the current markdown file in a browser window *([screenshot](https://user-images.githubusercontent.com/3920290/82754898-f7394600-9dc7-11ea-8278-2305363ed372.png))*
 *[`gitdiff_highlight`](https://github.com/vincens2005/lite-xl-gitdiff-highlight)** | highlight changed lines from git *([screenshot](https://raw.githubusercontent.com/vincens2005/lite-xl-gitdiff-highlight/master/screenshot.png))*
diff --git a/plugins/fontconfig.lua b/plugins/fontconfig.lua
new file mode 100644
index 0000000..a3e0f57
--- /dev/null
+++ b/plugins/fontconfig.lua
@@ -0,0 +1,91 @@
+-- mod-version:2 -- lite-xl 2.0
+local subprocess = require "process"
+
+local core = require "core"
+local style = require "core.style"
+local config = require "core.config"
+
+--[[
+  Example config (put it in user module):
+
+  ```
+  local fontconfig = require "plugins.fontconfig"
+  fontconfig.use {
+    font = { name = 'sans', size = 13 * SCALE },
+    code_font = { name = 'monospace', size = 13 * SCALE },
+  }
+  ```
+
+  if you want the fonts to load instantaneously on startup,
+  you can try your luck on fontconfig.use_blocking. I won't be responsible for
+  the slow startup time.
+]]
+
+local function resolve_font(spec)
+  local scan_rate = 1 / config.fps
+  local proc = subprocess.start({ "fc-match", "-s", "-f", "%{file}\n", spec }, {
+    stdin = subprocess.REDIRECT_DISCARD,
+    stdout = subprocess.REDIRECT_PIPE,
+    stderr = subprocess.REDIRECT_STDOUT
+  })
+  local prev
+  local lines = {}
+  while proc:running() do
+    coroutine.yield(scan_rate)
+    local buf = proc:read_stdout()
+    if type(buf) == "string" then
+      local last_line_start = 1
+      for line, ln in string.gmatch(buf, "([^\n]-)\n()") do
+        last_line_start = ln
+        if prev then line = prev .. line end
+        table.insert(lines, line)
+      end
+      prev = last_line_start < #buf and string.sub(buf, last_line_start)
+    end
+  end
+  if prev then table.insert(lines, prev) end
+
+  if proc:returncode() ~= 0 or #lines < 1 then
+    error(string.format("Cannot find a font matching the given specs: %q", spec), 0)
+  end
+  return lines[1]
+end
+
+
+local M = {}
+
+function M.load(font_name, font_size, font_opt)
+  local font_file = resolve_font(font_name)
+  return renderer.font.load(font_file, font_size, font_opt)
+end
+
+function M.load_blocking(font_name, font_size, font_opt)
+  local co = coroutine.create(function()
+    return M.load(font_name, font_size, font_opt)
+  end)
+  local result
+  while coroutine.status(co) ~= "dead" do
+    local ok, err = coroutine.resume(co)
+    if not ok then error(err) end
+    result = err
+  end
+  return result
+end
+
+function M.use(spec)
+  core.add_thread(function()
+    for key, value in pairs(spec) do
+      style[key] = M.load(value.name, value.size, value)
+    end
+  end)
+end
+
+-- there is basically no need for this, but for the sake of completeness
+-- I'll leave this here
+function M.use_blocking(spec)
+  for key, value in pairs(spec) do
+    style[key] = M.load_blocking(value.name, value.size, value)
+  end
+end
+
+return M