feat(picker): better integration with markview and render-markdown when previewing

lua/snacks/picker/core/preview.lua

@@ -428,17 +428,7 @@ function M:markdown()
   end
   local buf, win = self.win.buf, self.win.win ---@type number, number
 
-  vim.bo[buf].filetype = "markdown"
-  Snacks.image.doc.attach(buf)
-
-  if package.loaded["render-markdown"] then
-    require("render-markdown.core.ui").update(buf, win, "Snacks", true)
-  elseif package.loaded["markview"] then
-    local strict = package.loaded["markview"].strict_render
-    if strict then
-      strict:render(buf)
-    end
-  end
+  require("snacks.picker.util.markdown").render(buf, { win = win })
 end
 
 function M:spinner(enable)

lua/snacks/picker/util/markdown.lua

@@ -0,0 +1,85 @@
+local M = {}
+
+local ns = vim.api.nvim_create_namespace("snacks.picker.util.markdown")
+local did_setup = false
+
+---@private
+local function setup()
+  if did_setup then
+    return
+  end
+  did_setup = true
+
+  -- trigger plugin loading if available
+  pcall(require, "render-markdown")
+  pcall(require, "markview")
+end
+
+---@param buf number
+---@param opts? {images: boolean, win?: number}
+function M.render(buf, opts)
+  setup()
+  opts = opts or {}
+
+  local ft = vim.bo[buf].filetype
+  if not ft:find("^markdown") then
+    ft = ft:gsub("%.?markdown%.?", "")
+    -- set filetype to markdown but preserve existing ft as a suffix
+    -- use eventignore to avoid triggering autocmds
+    local ei = vim.o.eventignore
+    vim.o.eventignore = "all"
+    vim.bo[buf].filetype = table.concat({ "markdown", ft ~= "" and ft or "" }, ".")
+    vim.o.eventignore = ei
+  end
+
+  if not pcall(vim.treesitter.start, buf, "markdown") then
+    vim.bo[buf].syntax = "markdown"
+  end
+
+  if opts.images ~= false then
+    Snacks.image.doc.attach(buf)
+  end
+
+  if package.loaded["render-markdown"] then
+    local UI = require("render-markdown.core.ui")
+    local State = require("render-markdown.state")
+    local s = State.get(buf)
+    s.render_modes = true
+    s.resolved.modes = true
+    local wins = vim.fn.win_findbuf(buf)
+    for _, win in ipairs(wins) do
+      UI.update(buf, win, "Snacks", true)
+    end
+  elseif package.loaded["markview"] then
+    local strict = require("markview").strict_render
+    if strict then
+      strict:clear(buf)
+      strict:render(buf)
+    end
+  else
+    M.render_fallback(buf)
+  end
+end
+
+-- Fallback simple highlighting for headings and horizontal rules
+---@param buf number
+function M.render_fallback(buf)
+  vim.api.nvim_buf_clear_namespace(buf, ns, 0, -1)
+  local lines = vim.api.nvim_buf_get_lines(buf, 0, -1, false)
+  for l, line in ipairs(lines) do
+    local _, level = line:find("^#+()")
+    if level then
+      vim.api.nvim_buf_set_extmark(buf, ns, l - 1, 0, {
+        line_hl_group = "@markup.heading." .. tostring(level) .. ".markdown",
+      })
+    elseif line:find("^%-%-%-+%s*$") then
+      vim.api.nvim_buf_set_extmark(buf, ns, l - 1, 0, {
+        virt_text_win_col = 0,
+        virt_text = { { string.rep("-", vim.go.columns), "@punctuation.special.markdown" } },
+        priority = 100,
+      })
+    end
+  end
+end
+
+return M