Half-Arrowheads

For your information, the most recent version of BKChem was 0.12.0_pre3 at the time of writing.

Please, read this article to the end, because this method has some drawbacks.

As you might have noticed BKChem has built-in support for arrows. Unfortunalety, you can only create full and no half-arrowheads. That is one wedge below and one above instead of one below or above the arrow-line.

BKChem uses the “arrow” library that TK provides. Consequently, the limitation originates from TK, not BKChem itself.

However, you can create half-arrowheads with BKChem using the “vector graphics- polygon” tool.

• create an arrow to your liking
• remove the arrowhead via “RMB (Right Mouse Button) - Properties” or “MMB (Middle Mouse Button)” on the arrow
• in the “Configuration” window you deselect “Arrow-head on start/end” (depends on the arrow); click OK
• select the “vector graphics- polygon” tool
• LMB (Left Mouse Button) click on the end of the line, where the half-arrowhead should be; do another LMB to set the height of it
• RMB click on the line, so you have a 90° angle between the arrowhead and the line
• MMB on the polygon you just have created
• in the “Configuration” uncheck “Transparent” below the “Area color” box (now the greyish color of the “Area color” box sign should disappear)
• LMB on “Area color” box; a “Colour” window should appear
• select the same color as the arrowline has (note: If you select the color by using the figures, you have to press enter key at the last value you set. Clicking “OK”, without pressing enter key prior to that, equals a “Cancel” click. The same applies to the hexadecimal-number figure! The tab key works here, use it!); click OK; click OK
• polygon is filled with the color you have choosen before

This method can be very tedious, especially, if the half-arrowhead is very small. To fine tune the results select one corner of the wedge and move it with the cursor keys. Maybe move the wedge away from the line altogether and then rearrange the wedge with the cursor keys. You can copy-paste the arrowheads, so they look kind of identical.