Python EFL: Advanced Align Hints and Weight Control (2026)

Positioning widgets precisely is the difference between a amateur tool and a professional application. This Python EFL tutorial dives deep into Align Hints and Weight Control, showing you how to anchor widgets to specific parts of a window.

TL;DR: Alignment Summary

• Weight: Determines if a widget wants extra space.
• Align: Determines where the widget sits within that space (0.0 to 1.0).
• FILL: A special align hint that forces the widget to stretch across the available space.
• Core Goal: Learn to center, anchor, or stretch buttons using Evas hints.

Weight vs. Align: The Core Difference

In the Enlightenment Foundation Libraries (EFL), layout is a two-step process: 1. Weight (size_hint_weight): The container asks, “Does this widget need more room?” 2. Align (size_hint_align): If there is extra room, the container asks, “Where should I put the widget?”

Common Alignment Values

Code Example: Mastering Hints

This example shows three buttons with different weight and align configurations to demonstrate how they interact.

import efl.elementary as elm
from efl.elementary.box import Box
from efl.elementary.button import Button
from efl.elementary.window import StandardWindow
from efl.evas import EVAS_HINT_EXPAND, EVAS_HINT_FILL

# Constants
EXPAND_BOTH = EVAS_HINT_EXPAND, EVAS_HINT_EXPAND
FILL_BOTH = EVAS_HINT_FILL, EVAS_HINT_FILL

class MainWindow(StandardWindow):
    def __init__(self):
        StandardWindow.__init__(self, "ex3", "Weight & Align Demo", size=(300, 400))
        self.callback_delete_request_add(lambda o: elm.exit())

        # Button 1: No expansion, but fills its narrow row
        btn1 = Button(self)
        btn1.size_hint_weight = (0, 0)
        btn1.size_hint_align = FILL_BOTH
        btn1.text = "Fixed Size (Fill)"
        btn1.show()

        # Button 2: Fully expands and fills the window
        btn2 = Button(self)
        btn2.size_hint_weight = EXPAND_BOTH
        btn2.size_hint_align = FILL_BOTH
        btn2.text = "Expanding (Fill)"
        btn2.show()

        # Button 3: Anchored to the bottom-right
        btn3 = Button(self)
        btn3.size_hint_weight = EXPAND_BOTH
        btn3.size_hint_align = (1.0, 1.0) # Bottom Right
        btn3.text = "Anchored Corner"
        btn3.show()

        # Container
        our_box = Box(self)
        our_box.size_hint_weight = EXPAND_BOTH
        our_box.pack_end(btn1)
        our_box.pack_end(btn2)
        our_box.pack_end(btn3)
        our_box.show()

        self.resize_object_add(our_box)

if __name__ == "__main__":
    elm.init()
    gui = MainWindow()
    gui.show()
    elm.run()

Frequently Asked Questions (FAQ)

What happens if I set align without weight?

If weight is 0, the container won’t give the widget any extra space. Therefore, the align hint will have no visible effect because there is no room to “move” or “fill” within.

How do I perfectly center a button?

Set size_hint_weight to EXPAND_BOTH and size_hint_align to (0.5, 0.5). This gives the button all available space but forces it to sit exactly in the middle of that space.

Is EVAS_HINT_FILL a specific number?

Yes, in the underlying C library, EVAS_HINT_FILL is usually represented as -1.0. It acts as a flag to tell the layout engine to ignore margins and stretch the object.

Key Takeaways

• Weight creates space; Align uses it.
• Use (0.0, 0.0) to (1.0, 1.0) for fractional positioning.
• Combine these hints to create complex, responsive interfaces that look great on any screen size.