build: remove synctex test files

Problem: Okular settings path was incomplete and didn't mention the
trigger keybinding.

Solution: Update to full path (Settings -> Configure Okular -> Editor)
and note that Shift+click triggers inverse search.

README.md

@@ -1,6 +1,6 @@
 # preview.nvim
 
-**Universal document previewer for Neovim**
+**Universal previewer for Neovim**
 
 An extensible framework for compiling and previewing _any_ documents (LaTeX,
 Typst, Markdown, etc.)—diagnostics included.
@@ -81,3 +81,8 @@ vim.g.preview = {
   typst = { open = { 'sioyek', '--new-instance' } },
 }
 ```
+
+**Q: How do I set up SyncTeX (forward/inverse search)?**
+
+See `:help preview-synctex` for full recipes covering Zathura, Sioyek, and
+Okular.

doc/preview.txt

@@ -26,6 +26,7 @@ CONTENTS                                                   *preview-contents*
   7. Lua API ................................................... |preview-api|
   8. Events ............................................... |preview-events|
   9. Health ............................................... |preview-health|
+  10. SyncTeX ............................................. |preview-synctex|
 
 ==============================================================================
 REQUIREMENTS                                           *preview-requirements*
@@ -272,5 +273,116 @@ Checks: ~
 - Each configured provider's binary is executable
 - Each configured provider's opener binary (if any) is executable
 
+==============================================================================
+SYNCTEX                                                    *preview-synctex*
+
+SyncTeX enables bidirectional navigation between LaTeX source and the
+compiled PDF. The `latex` preset compiles with `-synctex=1` by default.
+
+Forward search (editor -> viewer) requires caching the output path.
+Inverse search (viewer -> editor) requires a fixed Neovim server socket.
+
+The following configs leverage the below basic setup: ~
+
+>lua
+    vim.fn.serverstart('/tmp/nvim-preview.sock')
+
+    local synctex_pdf = {}
+    vim.api.nvim_create_autocmd('User', {
+      pattern = 'PreviewCompileSuccess',
+      callback = function(args)
+        synctex_pdf[args.data.bufnr] = args.data.output
+      end,
+    })
+<
+
+The recipes below bind `<leader>s` for forward search. To scroll the PDF
+automatically on cursor movement, call the forward search function from a
+|CursorMoved| or |CursorHold| autocmd instead.
+
+Viewer-specific recipes: ~
+
+                                                    *preview-synctex-zathura*
+Zathura ~
+
+Inverse search: Ctrl+click.
+
+>lua
+    vim.keymap.set('n', '<leader>s', function()
+      local pdf = synctex_pdf[vim.api.nvim_get_current_buf()]
+      if pdf then
+        vim.fn.jobstart({
+          'zathura', '--synctex-forward',
+          vim.fn.line('.') .. ':0:' .. vim.fn.expand('%:p'), pdf,
+        })
+      end
+    end)
+
+    vim.g.preview = {
+      latex = {
+        open = {
+          'zathura',
+          '--synctex-editor-command',
+          'nvim --server /tmp/nvim-preview.sock'
+            .. [[ --remote-expr "execute('b +%{line} %{input}')"]],
+        },
+      },
+    }
+<
+
+                                                     *preview-synctex-sioyek*
+Sioyek ~
+
+Inverse search: right-click with synctex mode active.
+
+Add to `~/.config/sioyek/prefs_user.config`: >
+    inverse_search_command nvim --server /tmp/nvim-preview.sock --remote-expr "execute('b +%2 %1')"
+<
+
+>lua
+    vim.keymap.set('n', '<leader>s', function()
+      local pdf = synctex_pdf[vim.api.nvim_get_current_buf()]
+      if pdf then
+        vim.fn.jobstart({
+          'sioyek',
+          '--instance-name', 'preview',
+          '--forward-search-file', vim.fn.expand('%:p'),
+          '--forward-search-line', tostring(vim.fn.line('.')),
+          pdf,
+        })
+      end
+    end)
+
+    vim.g.preview = {
+      latex = {
+        open = { 'sioyek', '--instance-name', 'preview' },
+      },
+    }
+<
+
+                                                     *preview-synctex-okular*
+Okular ~
+
+Inverse search (Shift+click): one-time GUI setup via
+Settings -> Configure Okular -> Editor -> Custom Text Editor: >
+    nvim --server /tmp/nvim-preview.sock --remote-expr "execute('b +%l %f')"
+<
+
+>lua
+    vim.keymap.set('n', '<leader>s', function()
+      local pdf = synctex_pdf[vim.api.nvim_get_current_buf()]
+      if pdf then
+        vim.fn.jobstart({
+          'okular', '--unique',
+          ('%s#src:%d:%s'):format(pdf, vim.fn.line('.'), vim.fn.expand('%:p')),
+        })
+      end
+    end)
+
+    vim.g.preview = {
+      latex = { open = { 'okular', '--unique' } },
+    }
+<
+
 ==============================================================================
  vim:tw=78:ts=8:ft=help:norl:

flake.nix

@@ -19,9 +19,10 @@
     {
       formatter = forEachSystem (pkgs: pkgs.nixfmt-tree);
 
-      devShells = forEachSystem (pkgs: {
-        default = pkgs.mkShell {
-          packages = [
+      devShells = forEachSystem (
+        pkgs:
+        let
+          devTools = [
             (pkgs.luajit.withPackages (
               ps: with ps; [
                 busted
@@ -32,10 +33,38 @@
             pkgs.stylua
             pkgs.selene
             pkgs.lua-language-server
-            pkgs.plantuml
-            pkgs.mermaid-cli
           ];
-        };
-      });
+          okular-wrapped = pkgs.symlinkJoin {
+            name = "okular";
+            paths = [ pkgs.kdePackages.okular ];
+            nativeBuildInputs = [ pkgs.makeWrapper ];
+            postBuild = ''
+              wrapProgram $out/bin/okular \
+                --prefix XDG_DATA_DIRS : "${pkgs.gsettings-desktop-schemas}/share/gsettings-schemas/${pkgs.gsettings-desktop-schemas.name}" \
+                --prefix XDG_DATA_DIRS : "${pkgs.gtk3}/share/gsettings-schemas/${pkgs.gtk3.name}"
+            '';
+          };
+        in
+        {
+          default = pkgs.mkShell {
+            packages = devTools;
+          };
+          presets = pkgs.mkShell {
+            packages = devTools ++ [
+              pkgs.typst
+              pkgs.texliveMedium
+              pkgs.tectonic
+              pkgs.pandoc
+              pkgs.asciidoctor
+              pkgs.quarto
+              pkgs.plantuml
+              pkgs.mermaid-cli
+              pkgs.zathura
+              pkgs.sioyek
+              okular-wrapped
+            ];
+          };
+        }
+      );
     };
 }

lua/preview/presets.lua

@@ -115,6 +115,24 @@ local function parse_asciidoctor(output)
   return diagnostics
 end
 
+---@param output string
+---@return preview.Diagnostic[]
+local function parse_mermaid(output)
+  local lnum = output:match('Parse error on line (%d+)')
+  if not lnum then
+    return {}
+  end
+  local msg = output:match('(Expecting .+)') or 'parse error'
+  return {
+    {
+      lnum = tonumber(lnum) - 1,
+      col = 0,
+      message = msg,
+      severity = vim.diagnostic.severity.ERROR,
+    },
+  }
+end
+
 ---@type preview.ProviderConfig
 M.typst = {
   ft = 'typst',
@@ -313,19 +331,7 @@ M.mermaid = {
     return (ctx.file:gsub('%.mmd$', '.svg'))
   end,
   error_parser = function(output)
-    local diagnostics = {}
-    for line in output:gmatch('[^\r\n]+') do
-      local lnum = line:match('^%s*Parse error on line (%d+)')
-      if lnum then
-        table.insert(diagnostics, {
-          lnum = tonumber(lnum) - 1,
-          col = 0,
-          message = line,
-          severity = vim.diagnostic.severity.ERROR,
-        })
-      end
-    end
-    return diagnostics
+    return parse_mermaid(output)
   end,
   clean = function(ctx)
     return { 'rm', '-f', (ctx.file:gsub('%.mmd$', '.svg')) }