Change color entry widget UX

- Previous alpha value used in autofill
- Always filter non-hex input
- Autocomplete on enter
- Treat 1-2 digit input as grey colors
- Treat short input (3/4) as shorthand hex notation
- 8 digit hex with # no longer clipped when pasted
- Side effect: filtered input moves cursor forward

https://gitlab.com/inkscape/inkscape/issues/346

2 files changed, 65 insertions, 20 deletions

diff --git a/src/ui/widget/color-entry.cpp b/src/ui/widget/color-entry.cpp
index 619a7d515..804350c6b 100644
--- a/src/ui/widget/color-entry.cpp
+++ b/src/ui/widget/color-entry.cpp
@@ -22,12 +22,17 @@ ColorEntry::ColorEntry(SelectedColor &color)
     : _color(color)
     , _updating(false)
     , _updatingrgba(false)
+    , _prevpos(0)
+    , _lastcolor(0)
 {
     _color_changed_connection = color.signal_changed.connect(sigc::mem_fun(this, &ColorEntry::_onColorChanged));
     _color_dragged_connection = color.signal_dragged.connect(sigc::mem_fun(this, &ColorEntry::_onColorChanged));
+    signal_activate().connect(sigc::mem_fun(this, &ColorEntry::_onColorChanged));
+    get_buffer()->signal_inserted_text().connect(sigc::mem_fun(this, &ColorEntry::_inputCheck));
     _onColorChanged();
 
-    set_max_length(8);
+    // add extra character for pasting a hash, '#11223344'
+    set_max_length(9);
     set_width_chars(8);
     set_tooltip_text(_("Hexadecimal RGBA value of the color"));
 }
@@ -38,6 +43,13 @@ ColorEntry::~ColorEntry()
     _color_dragged_connection.disconnect();
 }
 
+void ColorEntry::_inputCheck(guint pos, const gchar * /*chars*/, guint n_chars)
+{
+    // remember position of last character, so we can remove it.
+    // we only overflow by 1 character at most.
+    _prevpos = pos + n_chars - 1;
+}
+
 void ColorEntry::on_changed()
 {
     if (_updating) {
@@ -50,33 +62,63 @@ void ColorEntry::on_changed()
     Glib::ustring text = get_text();
     bool changed = false;
 
-    // Coerce the value format to eight hex digits
-    if (!text.empty() && text[0] == '#') {
-        changed = true;
-        text.erase(0, 1);
-        if (text.size() == 6) {
-            // it was a standard RGB hex
-            unsigned int alpha = SP_COLOR_F_TO_U(_color.alpha());
-            text += Glib::ustring::format(std::hex, std::setw(2), std::setfill(L'0'), alpha);
+    // Coerce the value format to hexadecimal
+    for (auto it = text.begin(); it != text.end(); /*++it*/) {
+        if (!g_ascii_isxdigit(*it)) {
+            text.erase(it);
+            changed = true;
+        } else {
+            ++it;
         }
     }
 
+    if (text.size() > 8) {
+        text.erase(_prevpos, 1);
+        changed = true;
+    }
+
+    // autofill rules
     gchar *str = g_strdup(text.c_str());
     gchar *end = nullptr;
     guint64 rgba = g_ascii_strtoull(str, &end, 16);
-    if (end != str) {
-        ptrdiff_t len = end - str;
-        if (len < 8) {
+    ptrdiff_t len = end - str;
+    if (len < 8) {
+        if (len == 0) {
+            rgba = _lastcolor;
+        } else if (len <= 2) {
+            if (len == 1) {
+                rgba *= 17;
+            }
+            rgba = (rgba << 24) + (rgba << 16) + (rgba << 8);
+        } else if (len <= 4) {
+            // display as rrggbbaa
+            rgba = rgba << (4 * (4 - len));
+            guint64 r = rgba & 0xf000;
+            guint64 g = rgba & 0x0f00;
+            guint64 b = rgba & 0x00f0;
+            guint64 a = rgba & 0x000f;
+            rgba = 17 * ((r << 12) + (g << 8) + (b << 4) + a);
+        } else {
             rgba = rgba << (4 * (8 - len));
         }
-        _updatingrgba = true;
-        if (changed) {
-            set_text(str);
+
+        if (len == 7) {
+            rgba = (rgba & 0xfffffff0) + (_lastcolor & 0x00f);
+        } else if (len == 5) {
+            rgba = (rgba & 0xfffff000) + (_lastcolor & 0xfff);
+        } else if (len != 4 && len != 8) {
+            rgba = (rgba & 0xffffff00) + (_lastcolor & 0x0ff);
         }
-        SPColor color(rgba);
-        _color.setColorAlpha(color, SP_RGBA32_A_F(rgba));
-        _updatingrgba = false;
     }
+
+    _updatingrgba = true;
+    if (changed) {
+        set_text(str);
+    }
+    SPColor color(rgba);
+    _color.setColorAlpha(color, SP_RGBA32_A_F(rgba));
+    _updatingrgba = false;
+
     g_free(str);
 }
 
@@ -90,8 +132,8 @@ void ColorEntry::_onColorChanged()
     SPColor color = _color.color();
     gdouble alpha = _color.alpha();
 
-    guint32 rgba = color.toRGBA32(alpha);
-    Glib::ustring text = Glib::ustring::format(std::hex, std::setw(8), std::setfill(L'0'), rgba);
+    _lastcolor = color.toRGBA32(alpha);
+    Glib::ustring text = Glib::ustring::format(std::hex, std::setw(8), std::setfill(L'0'), _lastcolor);
 
     Glib::ustring old_text = get_text();
     if (old_text != text) {
diff --git a/src/ui/widget/color-entry.h b/src/ui/widget/color-entry.h
index 883076c7d..4df80def9 100644
--- a/src/ui/widget/color-entry.h
+++ b/src/ui/widget/color-entry.h
@@ -30,12 +30,15 @@ protected:
 
 private:
     void _onColorChanged();
+    void _inputCheck(guint pos, const gchar * /*chars*/, guint /*n_chars*/);
 
     SelectedColor &_color;
     sigc::connection _color_changed_connection;
     sigc::connection _color_dragged_connection;
     bool _updating;
     bool _updatingrgba;
+    guint32 _lastcolor;
+    int _prevpos;
 };
 
 }