General
This program is an extension that adds Windows file explorer support for generating thumbnails for DXF files. As of version 1.1, there is support for the following, most common DXF entities: POINT, LINE, LWPOLYLINE, POLYLINE (including polyface and polygon meshes), CIRCLE, ARC, ELLIPSE, SPLINE (with fit points and control points), TEXT and MTEXT, 3DFACE, SOLID, INSERT (BLOCK REFERENCE).
2D as well as 3D designs are supported but thumbnails always show top view, i.e. X-Y plane with the viewer on +Z axis.
This program is tested mainly on Windows 10 and roughly on Windows 11 for desktop PC. Testing on ARM devices is in future plans.
Quick Preparation
To use this program make sure that,
Thumbnails are enabled on your system. This is usually the default behavior, but if it does not work check the options explained below.
You must allow this app to execute in background. This is probably default but ensure that this is enabled in the settings of the app. Search the app in Apps & Features and click on "Advanced options". In app permissions enable the "Background apps" button (Win 10) or set the "Background apps permission" combo box at "Always" (Win 11).
Limitations
Besides not supported entities, like HATCH, 3DSOLID, DIMENSION e.t.c. (the viewer may read the rest of them not mentioned above in details in the DXF reference document by Autodesk) there are some limitations but for the purposes of a simple icon preview in most cases they are acceptable. The user must keep in mind though that the icon thumbnail may be not an exact preview of the DXF model. Shortly, styles are ignored, such as line styles and text styles and views other than the model view.
How it works
Windows automatically show thumbnail icons on files by calling the corresponding thumbnail handler program if there is one. To enable this in file explorer's view tab, simply select one of the icon view (large - extra large) and in case nothing happens make sure that the thumbnail preview is not disabled. In Folder Options (View Tab) search for a tick "Always show icons, never thumbnails" and uncheck it. Also, there is an option in Advanced System Settings (Advanced Tab, Performance Settings), check the option "Show thumbnails instead of icons".
As soon as there are new DXF files in icon view, file explorer should automatically call the handler and create the thumbnails for you. Just be patient for the first time it might take awhile, depending on the DXF content complexity, the size and number of the files inside a folder. Every time a new DXF file or an existing one is saved, the modification time will change and this will trigger a new generation of thumbnail icon.
All thumbnails of your system are cached in special storage. The cache is useful in case of already generated icons, for faster preview, but if one needs to update them all, especially the old ones, for example if a new handler is installed, you must clear the cache. Please note that this will erase all the thumbnails of your disk not just for DXF files, but the associated programs for each file extension should recreate them again with no problem. The cache can be found and deleted in Disk Cleanup utility. The list with "Files to delete" shows at the bottom an entry "Thumbnails".
Troubleshooting
There are two types of problem that can be identified and some tips to solve it:
One or more thumbnails are totally blank (black) without DXF logo on them. If a thumbnail has not the DXF logo, it means that the generation failed. It could be either by Windows failure or by specific app's failure. For example, if all of the thumbnails inside a folder are blank, this is usually a file explorer refresh issue, you may try change the icon view e.g. to details and back to icons, or leave the current folder and enter back. If only few of them are blank you can try individual thumbnail creation. Simply open and resave the DXF file (just a text editor will do) in order to change its modification time and Windows will automatically call the handler again. If the thumbnail is shown correctly then it was a temporary explorer error. If not, it is probably an app's error.
One or more thumbnails have blank content but with the DXF logo on them. If the DXF logo is drawn the file is parsed correctly but the content in the file may be incompatible with this app or it could be a bug. In this case, check the limitations above and the file's content.
If you experience wrong thumbnail preview of a specific DXF file taking into account the aforementioned limitations, nothing would help more than the file itself. If you think you could share a sample that should be displayed correctly but it does not, feel free to upload it here in order to help improving this software.