begin work on custom theme support

ui/theme/themefile.go

@@ -0,0 +1,115 @@
+package theme
+
+import (
+	"encoding/hex"
+	"errors"
+	"fmt"
+	"image/color"
+	"os"
+	"strings"
+
+	"github.com/dweymouth/supersonic/sharedutil"
+	"github.com/pelletier/go-toml"
+)
+
+type ThemeFileHeader struct {
+	Name          string
+	Version       string
+	SupportsDark  bool
+	SupportsLight bool
+}
+
+type ThemeFile struct {
+	SupersonicTheme ThemeFileHeader
+
+	DarkColors  ThemeColors
+	LightColors ThemeColors
+}
+
+type ThemeColors struct {
+	// Supersonic-specific colors
+
+	PageBackground string
+
+	// Fyne colors
+
+	Background string
+
+	Button string
+
+	DisabledButton string
+
+	Disabled string
+
+	Error string
+
+	Focus string
+
+	Foreground string
+
+	Hover string
+
+	InputBackground string
+
+	InputBorder string
+
+	MenuBackground string
+
+	OverlayBackground string
+
+	Placeholder string
+
+	Pressed string
+
+	Primary string
+
+	ScrollBar string
+
+	Selection string
+
+	Separator string
+
+	Shadow string
+
+	Success string
+
+	Warning string
+}
+
+func ReadThemeFile(filePath string) (*ThemeFile, error) {
+	f, err := os.Open(filePath)
+	if err != nil {
+		return nil, err
+	}
+	defer f.Close()
+
+	theme := &ThemeFile{}
+	if err := toml.NewDecoder(f).Decode(theme); err != nil {
+		return nil, err
+	}
+
+	if theme.SupersonicTheme.Name == "" || theme.SupersonicTheme.Version != "0.1" {
+		return nil, errors.New("invalid theme file name or version")
+	}
+	if !(theme.SupersonicTheme.SupportsDark || theme.SupersonicTheme.SupportsLight) {
+		return nil, errors.New("invalid theme file: must support one or both of light/dark")
+	}
+
+	return theme, nil
+}
+
+// Parses a CSS-style #RRGGBB or #RRGGBBAA string
+func ColorStringToColor(colorStr string) (color.Color, error) {
+	if !strings.HasPrefix(colorStr, "#") || !sharedutil.SliceContains([]int{7, 9}, len(colorStr)) {
+		return color.Black, errors.New("invalid color string")
+	}
+	colorBytes := make([]byte, 4)
+	n, err := hex.Decode(colorBytes, []byte(colorStr[1:]))
+	if err != nil {
+		return color.Black, fmt.Errorf("invalid color string: %s", err.Error())
+	}
+	if n == 3 {
+		colorBytes[3] = 255 // opaque alpha
+	}
+	return color.RGBA{R: colorBytes[0], G: colorBytes[1], B: colorBytes[2], A: colorBytes[3]}, nil
+}