`NppTbData.pszModuleName` is not properly assigned when Markdown panel is docked

[rdipardo]

A forum user asked a while ago why N++'s built-in Docking Manager never reloads the MarkdownViewer++ panel when the application starts. This goes for NppMarkdownPanel as well, and for the same reason, so I'm cross-posting nea/MarkdownViewerPlusPlus#159.

The problem is the plugin's module name is serialized without a file extension. N++ fails to locate the module on disk, so never calls NppMarkdownPanel.MarkdownPanelController.TogglePanelVisible() when starting up.

See what happens when the file extension is written to config.xml as the TogglePanelVisible method should be doing.

1. Click Toggle Markdown Panel and leave the panel showing
2. Quit Notepad++
3. Open %AppData%\Notepad++\config.xml (if you have a system-wide installation), or the config.xml inside your portable installation
4. Notice that NppMarkdownPanel.Main.ModuleName is the value of the pluginName attribute, e.g.,

<GUIConfig name="DockingManager" leftWidth="200" rightWidth="664" topHeight="200" bottomHeight="200">
    <PluginDlg pluginName="NppMarkdownPanel" id="0" curr="1" prev="-1" isVisible="yes" />
    <!-- . . . -->
</GUIConfig>

5. Edit the XML to pluginName="NppMarkdownPanel.dll", i.e., append the module's file extension; make sure isVisible remains "yes"
6. Start Notepad++
7. The panel is automatically opened

A tiny patch is all that's needed to make this the default behaviour:

--- a/NppMarkdownPanel/MarkdownPanelController.cs
+++ b/NppMarkdownPanel/MarkdownPanelController.cs
@@ -298 +298 @@ namespace NppMarkdownPanel
-                _nppTbData.pszModuleName = Main.ModuleName;
+                _nppTbData.pszModuleName = $"{Main.ModuleName}.dll";