Add support for alpha channel in colors
This makes it easier to define faces that lighten/darken whatever they apply on.
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c6906be475
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@ -6,9 +6,9 @@ A 'face' refers how the specified text is displayed, it has a foreground
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color, a background color, and some attributes. The value of a face has the
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following format:
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---------------------------------------
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-----------------------------------------
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[fg_color][,bg_color][+attributes][@base]
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---------------------------------------
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-----------------------------------------
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'fg_color', 'bg_color'::
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a color whose value can be expressed in the following formats:
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@ -20,7 +20,11 @@ following format:
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keep the existing color
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*rgb:RRGGBB*:::
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hexadecimal value
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*rgba:RRGGBBAA*:::
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hexadecimal value
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if unspecified, *default* is used.
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Alpha values are used to blend the face onto either its base or the existing
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color. For technical reasons alpha values must be >16 if specified.
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'attributes'::
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string whose individual letters set an attribute:
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21
src/color.cc
21
src/color.cc
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@ -34,6 +34,13 @@ bool is_color_name(StringView color)
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return contains(color_names, color);
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}
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void Color::validate_alpha()
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{
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static_assert(RGB == 17);
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if (a < RGB)
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throw runtime_error("Colors alpha must be > 16");
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}
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Color str_to_color(StringView color)
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{
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auto it = find_if(color_names, [&](const char* c){ return color == c; });
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@ -55,6 +62,11 @@ Color str_to_color(StringView color)
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return { (unsigned char)(hval(color[4]) * 16 + hval(color[5])),
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(unsigned char)(hval(color[6]) * 16 + hval(color[7])),
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(unsigned char)(hval(color[8]) * 16 + hval(color[9])) };
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if (color.length() == 13 and color.substr(0_byte, 5_byte) == "rgba:")
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return { (unsigned char)(hval(color[5]) * 16 + hval(color[6])),
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(unsigned char)(hval(color[7]) * 16 + hval(color[8])),
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(unsigned char)(hval(color[9]) * 16 + hval(color[10])),
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(unsigned char)(hval(color[11]) * 16 + hval(color[12])) };
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throw runtime_error(format("unable to parse color: '{}'", color));
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return Color::Default;
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@ -62,10 +74,13 @@ Color str_to_color(StringView color)
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String to_string(Color color)
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{
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if (color.color == Color::RGB)
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if (color.isRGB())
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{
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char buffer[11];
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sprintf(buffer, "rgb:%02x%02x%02x", color.r, color.g, color.b);
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char buffer[14];
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if (color.a == 255)
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sprintf(buffer, "rgb:%02x%02x%02x", color.r, color.g, color.b);
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else
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sprintf(buffer, "rgba:%02x%02x%02x%02x", color.r, color.g, color.b, color.a);
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return buffer;
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}
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else
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25
src/color.hh
25
src/color.hh
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@ -3,6 +3,7 @@
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#include "hash.hh"
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#include "meta.hh"
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#include "assert.hh"
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namespace Kakoune
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{
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@ -12,7 +13,7 @@ class StringView;
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struct Color
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{
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enum NamedColor : char
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enum NamedColor : unsigned char
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{
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Default,
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Black,
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@ -34,15 +35,27 @@ struct Color
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RGB,
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};
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NamedColor color;
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union
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{
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NamedColor color;
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unsigned char a;
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};
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unsigned char r = 0;
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unsigned char g = 0;
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unsigned char b = 0;
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constexpr bool isRGB() const { return a >= RGB; }
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constexpr Color() : Color{Default} {}
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constexpr Color(NamedColor c) : color{c} {}
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constexpr Color(unsigned char r, unsigned char g, unsigned char b)
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: color{RGB}, r{r}, g{g}, b{b} {}
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constexpr Color(unsigned char r, unsigned char g, unsigned char b, unsigned char a = 255)
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: a{a}, r{r}, g{g}, b{b}
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{
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validate_alpha();
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}
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private:
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void validate_alpha();
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};
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constexpr bool operator==(Color lhs, Color rhs)
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@ -66,8 +79,8 @@ bool is_color_name(StringView color);
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constexpr size_t hash_value(const Color& val)
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{
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return val.color == Color::RGB ?
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hash_values(val.color, val.r, val.g, val.b)
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return val.isRGB() ?
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hash_values(val.a, val.r, val.g, val.b)
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: hash_value(val.color);
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}
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@ -2328,7 +2328,7 @@ const CommandDesc set_face_cmd = {
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"set-face <scope> <name> <facespec>: set face <name> to refer to <facespec> in <scope>\n"
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"\n"
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"facespec format is <fg color>[,<bg color>][+<attributes>][@<base>]\n"
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"colors are either a color name, or rgb:###### values.\n"
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"colors are either a color name, rgb:######, or rgba:######## values.\n"
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"attributes is a combination of:\n"
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" u: underline, i: italic, b: bold, r: reverse,\n"
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" B: blink, d: dim,\n"
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10
src/face.hh
10
src/face.hh
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@ -50,6 +50,14 @@ struct Face
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inline Face merge_faces(const Face& base, const Face& face)
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{
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auto alpha_blend = [](Color base, Color color) {
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auto blend = [&](unsigned char Color::*field) {
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int blended = (base.*field * (255 - color.a) + color.*field * color.a) / 255;
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return static_cast<unsigned char>(blended <= 255 ? blended : 255);
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};
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return Color{blend(&Color::r), blend(&Color::g), blend(&Color::b), base.a};
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};
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auto choose = [&](Color Face::*color, Attribute final_attr) {
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if (face.attributes & final_attr)
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return face.*color;
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@ -57,6 +65,8 @@ inline Face merge_faces(const Face& base, const Face& face)
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return base.*color;
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if (face.*color == Color::Default)
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return base.*color;
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if ((base.*color).isRGB() and (face.*color).isRGB() and (face.*color).a != 255)
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return alpha_blend(base.*color, face.*color);
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return face.*color;
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};
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@ -252,7 +252,7 @@ int NCursesUI::Palette::get_color(Color color)
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return it->value;
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else if (m_change_colors and can_change_color() and COLORS > 16)
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{
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kak_assert(color.color == Color::RGB);
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kak_assert(color.isRGB());
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if (m_next_color > COLORS)
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m_next_color = 16;
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init_color(m_next_color,
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@ -264,7 +264,7 @@ int NCursesUI::Palette::get_color(Color color)
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}
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else
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{
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kak_assert(color.color == Color::RGB);
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kak_assert(color.isRGB());
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int lowestDist = INT_MAX;
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int closestCol = -1;
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for (int i = 0; i < std::min(256, COLORS); ++i)
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@ -127,7 +127,7 @@ private:
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void write_field(Color color)
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{
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write_field(color.color);
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if (color.color == Color::RGB)
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if (color.isRGB())
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{
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write_field(color.r);
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write_field(color.g);
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@ -305,7 +305,7 @@ struct MsgReader::Reader<Color> {
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{
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Color res;
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res.color = Reader<Color::NamedColor>::read(reader);
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if (res.color == Color::RGB)
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if (res.isRGB())
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{
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res.r = Reader<unsigned char>::read(reader);
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res.g = Reader<unsigned char>::read(reader);
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