High DPI in Lazarus 1.8 and above
To handle High DPI using new features in 1.8, follow these steps:
On Windows: enable DPI awareness in Project Options -> Application. Decide if you want to support per monitor DPI awareness or not.
Enable LCL scaling for your application DPI awareness in Project Options -> Application -> "Use LCL scaling (Hi-DPI).
Set TForm.Scaled=True for all your forms (it is the default value). All WYSIWYG should work automatically. Also the designer scales the forms accordingly.
If you create controls run-time, scale all coordinates, sizes etc that have to be DPI-aware with TControl.Scale96ToForm() or ScaleDesignToForm() (depending on your choice of default PPI) or prepare your container (e.g. panel with controls) as it was with 96 PPI and then call TControl.AutoAdjustLayout(lapAutoAdjustForDPI, 96, ParentFormOfTheContainer.PixelsPerInch, 0, 0);
If some of your components don't scale their inner sizes, override DoAutoAdjustLayout and scale the sizes (see TToolBar) - it has to be done for all controls. If a LCL control misses DoAutoAdjustLayout please report to mantis and provide a patch if you can.