I want to add a callback to Variable, so I can update widget's attribute effected. about kiwi HOT 15 CLOSED

You can also set an override flag on your widget, and check that before applying the constraint variable values. If the flag is set, ignore the constraint values and use the override values. There's lot's of ways you could solve this without hacking into the kiwi source.

from kiwi.

context is there for you store anything you want to be associated with a variable. It can be any Python object, so storing a function there would be fine.

from kiwi.

What I want is a way to update effected widgets attributes when variable's value changed. I can think of two ways:
1, Associate the widget attribute with variable with context attribute, and iterate solver->m_impl->m_vars and apply variable value to widget attribute, after calling updateVariables.
2, Hack Variable::setValue method to set the value to widget attribute immediately.

Either way, I need to hack kiwi's source code somehow.

from kiwi.

What widgets are you talking about, and what attribute do you want to set?

If you are using Kiwi directly on your own, you know when you call updateVariables, so you can just iterate your variables then. If you are talking about Enaml's widgets, you may be better off hooking into its layout system rather than hacking Kiwi's source.

Basically, I need to know more about what you are trying to do before I can give you better advice.

from kiwi.

I'm using kiwi on my own, and I want to only update the variables that are constrained rather than all the variables defined by widget.
For example, each widget defines left, top, width, height, but for some widgets I only add a constraint for width and height, and want to set the left and top manually.
So I can only iterate the variables in solver->m_impl->m_rows rather than all the variables defined by the widgets.

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PS, I find that there is a problem with solver->m_impl->m_vars, is that it's never get removed except when reset the solver. So If I keep adding and removing constraints, the m_vars keep growing.

from kiwi.

m_impl is private and not part of the public API.

from kiwi.

If you want to set left and top of your widgets manually, you are free to do so. I'm not really seeing how this is an issue with Kiwi.

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The problem is I have no way to know which variable is constrained and which not (except through private m_impl->m_rows I guess).

If I choose the enaml way to do this, then the left and top would be reseted to zero every time re-layout:

        """ Update the geometry of the underlying toolkit widget.
        This should not be called directly by user code.
        """
        d = self.constrainable()
        x = d.left.value()
        y = d.top.value()
        w = d.width.value()
        h = d.height.value()
        self.set_geometry(x, y, w, h)

from kiwi.

I've changed Variable's initial value to NAN, and set the value to NAN if not found in m_rows, so I can detect the un-constrained variables.
Here's the diff in case you are interested.

diff --git a/libs/kiwi/kiwi/solverimpl.h b/libs/kiwi/kiwi/solverimpl.h
index 33b0711..fd517cc 100644
--- a/libs/kiwi/kiwi/solverimpl.h
+++ b/libs/kiwi/kiwi/solverimpl.h
@@ -10,6 +10,7 @@
 #include <limits>
 #include <memory>
 #include <vector>
+#include <cmath>
 #include "constraint.h"
 #include "errors.h"
 #include "expression.h"
@@ -305,7 +306,7 @@ public:
            Variable& var( const_cast<Variable&>( var_it->first ) );
            row_iter_t row_it = m_rows.find( var_it->second );
            if( row_it == row_end )
-               var.setValue( 0.0 );
+               var.setValue( NAN );
            else
                var.setValue( row_it->second->constant() );
        }
diff --git a/libs/kiwi/kiwi/variable.h b/libs/kiwi/kiwi/variable.h
index 525f434..e4de813 100644
--- a/libs/kiwi/kiwi/variable.h
+++ b/libs/kiwi/kiwi/variable.h
@@ -8,6 +8,7 @@
 #pragma once
 #include <memory>
 #include <string>
+#include <cmath>
 #include "shareddata.h"


@@ -91,13 +92,13 @@ private:
            SharedData(),
            m_name( name ),
            m_context( context ),
-           m_value( 0.0 ) {}
+           m_value(NAN) {}

        VariableData( const char* name, Context* context ) :
            SharedData(),
            m_name( name ),
            m_context( context ),
-           m_value( 0.0 ) {}
+           m_value(NAN) {}

        ~VariableData() {}

from kiwi.

You said you are using kiwi on your own. So you should know if the variables are constrained or not because you added them to the solver.

from kiwi.

You can also just added a constraint for the left and top values to constrain them to what you want e.g.: left == 42, top == 78

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Updating a constraint is more expensive, since it could be an animation or scrollview updating it every frame.
Traversing the constraint structure to find out what variables it uses is doable i think.

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Setting a flag is another useful feature I think, but I still think checking the NAN is a good default behaviour, thanks for your suggestions ;D

from kiwi.

Checking for NAN values doesn't cover a situation where constraints have been added and then removed later. The variables may still be underconstrained..

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