References: https://todo.sr.ht/~eliasnaur/gio/500

diff --git a/widget/material/theme.go b/widget/material/theme.go
index 3da7f4e7..0ed497a6 100644
--- a/widget/material/theme.go
+++ b/widget/material/theme.go
@@ -58,8 +58,8 @@ func NewTheme() *Theme {
        t.Palette = Palette{
                Fg:         rgb(0x000000),
                Bg:         rgb(0xffffff),
-               ContrastBg: rgb(0x3f51b5),
-               ContrastFg: rgb(0xffffff),
+               ContrastBg: rgb(0xdfdbd8),
+               ContrastFg: rgb(0x000000),

I'm wondering if the use of device-independent percentage-based
coordinate system (as is used in giocanvas) would be useful.


On Wed, Nov 10, 2021 at 1:04 PM Christophe Meessen
<christophe@meessen.net> wrote:
>
> Hello Chris
>
> I agree that the low level interface for raw op.Ops should stay in Px
> unit and float32. I’m only concerned about the end user API, the one
> that must be the most simple, efficient and stable.
>
> You asked me what I would suggest in place of unit.Value. I suggest to

Now that the changes have been made, here is a quick report on
updating giocanvas with the new API.   Originally, giocanvas has
several functions that perform transforms like this:

// AbsTranslate moves current location by (x,y)
func (c *Canvas) AbsTranslate(x, y float32) op.StateOp {
    ops := c.Context.Ops
    op.InvalidateOp{}.Add(ops)
    stack := op.Save(ops)
    tr := f32.Affine2D{}
    tr = tr.Offset(f32.Pt(x, y))
    op.Affine(tr).Add(ops)
    return stack
}

Re: SVG API -- I'm not a fan either, but it has the advantage of familiarity.
Re: Arcs like the existing Loader (older version), see:

https://github.com/ajstarks/giocanvas/blob/74de31426979ddf304fcd6701c5a057d2a0b13b7/abs.go#L246-L284

Re: Use cases for arc: (both circular and elliptical)

1) making a stroked arc
2) making a "wedge" shape (as seen in pie charts)

the elements are for making the arc:

1) center point
2) width, height

The giocanvas package now includes a charting package,
giocanvas/chart.  It supports line, area, scatter, and bar charts,
with titles and configurable axes.

The package reads data into a ChartBox structure (name, value pairs
(tab-separated) with metadata).

type ChartBox struct {
    Title                    string
    Data                     []NameValue
    Color                    color.RGBA
    Top, Bottom, Left, Right float64
    Minvalue, Maxvalue       float64
    Zerobased                bool

Note that giocanvas has buggy, incomplete version Arc code (see the
method AbsArc).  Fixes welcomed.

Thanks for the kind words.   FYI, the code that made the screen in the
README is at https://github.com/ajstarks/giocanvas/blob/master/play/main.go

On Thu, Jun 4, 2020 at 6:48 PM <dolanor@evereska.org> wrote:
>
> > After two weeks, here is the progress to date:
> > https://github.com/ajstarks/giocanvas
>
> I haven't looked at the API yet. But just the result in the README makes me wanna play with it already.
>
> Great job!
>
> I have worked on an SVG project for 3 months end of 2019, but it was on C#. So, this tickles my curiosity!

+1 on this proposal.


On Thu, Jun 4, 2020 at 3:07 PM Viktor Ogeman <viktor.ogeman@gmail.com> wrote:
>
> Hi,
>
> I am in need of transforms that include scaling, and find a TODO in the src
> showing that this is on the table. If there is interest I would be
> willing to try
> to send a first patch implementing this.
> Before I begin though it would be good to get clarification on a few items:
>
> 1. Still interest in getting this implemented?

After two weeks, here is the progress to date:
https://github.com/ajstarks/giocanvas

As discussed in the May community call, here are my notes on a general
canvas-like 2D API

# Notes on a general 2D API

## Introduction and Motivation

The principle is to keep the number of methods small and consistent,
using a common set of arguments for
location (x, y), and dimensions (w, h).

## Coordinate System

The coordinate system follows the traditional convention you learned in school: