kicad-developers team mailing list archive

[Tomasz Wlostowski <tomasz.wlostowski@xxxxxxx>]

On 08/12/2013 04:24 PM, Dick Hollenbeck wrote:
> Unfortunately, I guess I am losing my hope that we have a unified vision.
>
> We apparently do not.
>
> The project is based on wx.  The portions of wx that are objectionable, to me are:

Dick, Wayne,

I said I'd prefer to not use wxEvtHandler for deriving the tools from, 
but the tool framework code is at a proposal stage, so everything can be 
changed.

I did my own event system, because I wanted to test some concepts (such 
as FSM state switching and coroutines) which are orthogonal to any UI 
library. I'm not a wxWidgets guru, and perhaps most of my requirements 
could be met with some hacking of the wx's event system - I'm asking for 
your help here. The reasons why I didn't use wxEvent/wxEvtHandler right 
away are below:

- wxEvtHandler specifies a single method for handling events:

virtual bool ProcessEvent().

My idea was to have states in separate methods. One reason is avoid 
enumerating states (and a big switch() statement in 
MY_TOOL::ProcessEvent()), another is that with states in methods, FSMs 
could be easily specialized by inheritance. I guess it should be 
possible to do the same using a wxEventHandler. The base tool class 
derived from wxEvtHandler could implement its own ProcessEvent() with 
reworked dispatching code from TOOL_MANAGER, that calls the actual state 
handlers and/or wakes them coroutines.

- AFAIK wx uses integer IDs for defining UI commands. These IDs should 
to be globally unique, which may be hard to meet, as the project grows 
and many people contribute tool plugins. I chose to call tools by name. 
I'm fine with wxEvents if we find a way to ensure that all IDs (also 
across plugins) are easy to register and unique (hashes?).

- wx mouse events work in window space, tools work in board space:

I assumed that events passed to the tools will be adjusted to the 
current state of the view. For example if the view is being 
auto-scrolled (because the mouse is
near the edge), the tools should receive a series of mouse motion events 
because the cursor moves with respect to the world. Probably overloading 
wxMouseEvent could fix it, but this brings extra complexity too. In wx, 
mouse events are in screen space (GetLogicalPosition works for wxDC, but 
not for the GAL which has a non-wx-related coordinate system) - so the 
adjustment will have to be done in each state handler method or through 
some global event filter. The former is not too elegant, and I don't 
know if the latter is possible. You have much more experience with 
wxWidgets than me - what do you think about this? Then, there is a 
problem of distinguishing between events with board-relative coordinates 
with plain wx mouse events that might be injected from other sources 
(scripts). Also, tools should be able to request mouse snapping to 
nearby objects/grid and. It could be done on event level, by adjusting 
cursor coordinates accordingly.

- Drag vs click filtering:

Wx gives raw events. A click with a tiny mouse movement is considered a 
drag, unless some filtering is applied, so an intermediate event filter 
is required. I did it in TOOL_DISPATCHER class - maybe it could be 
integrated into wx event stack and work on wxEvent derivatives?

- No idea how wx event stack will play with coroutines:

One of the key points of my proposal was the ability to handle events in 
a loop, a thing that we consider really useful and simplifying tool 
development (a small demo is in pcbnew/tools/selection_tool.cpp in 
kicad-gal-orson branch). Is it possible to marry coroutines with the wx 
event system? It would be great if so, otherwise, me & Orson would miss 
them very much (after all, P&S and interactive selection tools that we 
are developing are the most complex ones, that really benefit from all 
goodies of the tool framework...).

- Wanted to avoid translating between VECTOR2<>/BOX2<> and 
wxRect/wxPoint in the tools.

- (a less technical one) I'm slightly biased against wx, so I didn't 
want to depend too much on it:
  * Different way of handling events on different plaforms: Let me give 
an example - the selection tool opens a pop-up menu when multiple items 
are clicked. We wanted to add some visual feedback that draws a bright, 
contrast border of the item you're about to select from the 
clarification menu. Then we discovered that it doesn't work on Windows: 
under Linux, a menu choice event comes after a menu close event, on 
Windows the order is opposite. I don't know if wx provides a mechanism 
for filtering and reordering events and if it can be adapted to fix such 
issues.
  * Mouse warping is forbidden on some OSes: emulate it (transparently 
to the tools, so mouse events need to be adjusted somewhere) or drop it. 
Existing Kicad tools use mouse warping quite frequently, so it's an 
important issue.
  * Linux issues: printing never, ever worked for me and the 
never-ending story of incompatible versions, which gave me bad feelings 
about general quality of the wxWidgets project and its packages in 
different distros.

Regards,
Tom