Brightness | Using Brightness Controller , you can control brightness | Model View Controller library

From the filter specification:

A computed value of other than none results in the creation of a stacking context [CSS21] the same way that CSS opacity does.

Then from another specification you can find the "painting order" of the elements:

Within each stacking context, the following layers are painted in back-to-front order:

1. the background and borders of the element forming the stacking context.
2. the child stacking contexts with negative stack levels (most negative first).
3. the in-flow, non-inline-level, non-positioned descendants.
4. the non-positioned floats.
5. the in-flow, inline-level, non-positioned descendants, including inline tables and inline blocks.
6. the child stacking contexts with stack level 0 and the positioned descendants with stack level 0.
7. the child stacking contexts with positive stack levels (least positive first).

Without filter, your element will get painted at step (3) since it doesn't create a stacking context. So it's under the position:absolute element painted at (6)

With filter, your element will also get painted at step (6) and in this case, the tree order will be considered to know which one will get painted first so it will end above the position:absolute one.

You can follow the specification to get more precise detail of each step.

Your question raises an important issue in C programming and in programming in general: does the program behave as expected in all cases?

The expression (brightness * maxval) / 100 computes an intermediary value brightness * maxval that may exceed the range of the type used to compute it. In Python and some other languages, this is not an issue because integers do not have a restricted range, but in C, C++, java, javascript and many other languages, integer types have a fixed number of bits so the multiplication can exceed this range.

It is the programmer's responsibility to ascertain that the range of the operands ensures that the multiplication does not overflow. This requires a good understanding of the integer promotion and conversion rules, which vary from one language to another and are somewhat tricky in C, especially with operands mixing signed and unsigned types.

In your particular case, both brightness and maxval have a type smaller than int so they are promoted to int with the same value and the multiplication produces an int value. If brightness is a percentage in the range 0 to 100, the result is in the range 0 to 25500, which the C Standard guarantees to be in the range of type int, and dividing this number by 100 produces a value in the range 0 to 100, in the range of int, and also in the range of the destination type uint8_t, so the operation is fully defined.

Whether this process should be documented in a comment or verified with debugging assertions is a matter of local coding rules. Changing the order of the operands to maxval * brightness / 100 and possibly using more explicit values and variable names might help the reader:

As the deprecated message says:

Assuming hiding is ok:

I think you should use Shared preferences for better state management. However, with this library, you can try the reset() function.

After calling reset(), calling isFirstRun() will return true as long as the app is running. After a restart, it will return false again. The first call of isFirstCall() will return true, subsequent calls will return false again.

You need to apply the animation to the pseudo-element as well.

I would recommend you to read this: https://docs.flutter.dev/development/ui/interactive.

But, answering your questions:

1. Error at line 157: Your Settings class is a stateless widget, so.. you can't set any state to that widget because it doesn't have state. If you want to add state you need to make Settings a Stateful Widget.

2. Error at line 169: as your Settings class extends from Stateless widget, it's super also doesn't have initState method. Again, you should make your Settings class a stateful widget.

3. Error in sharedpreferences: getString method can be null, so its type is String, meanwhile username is required, so you have these options:

Opt 1:

You should consider using different name for both classes. Also, for 2nd Settings class the message is clear:

Try adding either an explicit non-'null' default value or the 'required' modifier.dartmissing_default_value_for_parameter

so, Settings become:

We may draw the text on black background, and use alphamerge for creating transparent background with colored gradient text.
Then we can overlay the gradient (with the transparent background) on the input video.

I don't know if my suggested solution is the most elegant, but it is not lower the brightness of the gradient picture.

The suggested solution applies the following stages:

• Define synthetic black video source (1 frame).
• Draw white text on the black video frame.
• Add the "white text on black background" as alpha channel of the gradient image.
  Only the white text is opaque, and the black background is fully transparent.
• Overlay the above frame over the video.

Start by creating synthetic yellow video file (with sine audio) for testing: