[vte] emulation: Implement XTERM_SMGRAPHICS sequence

[Christian Persch <chpe src gnome org>]

commit be953b92769cfeab1fdddc84676f8bb1ae8f57b5
Author: Christian Persch <chpe src gnome org>
Date:   Fri Oct 23 19:55:05 2020 +0200

    emulation: Implement XTERM_SMGRAPHICS sequence

 src/parser-reply.hh  |   1 +
 src/parser-seq.py    |   4 +-
 src/sixel-context.hh |   4 +-
 src/vtedefines.hh    |   2 +
 src/vteseq.cc        | 117 +++++++++++++++++++++++++++++++++++++++++++++++++--
 5 files changed, 121 insertions(+), 7 deletions(-)
---
diff --git a/src/parser-reply.hh b/src/parser-reply.hh
index 81e1b516..2dfc2240 100644
--- a/src/parser-reply.hh
+++ b/src/parser-reply.hh
@@ -30,6 +30,7 @@ _VTE_REPLY(XTERM_MOUSE_EXT_SGR_REPORT_BUTTON_PRESS,   CSI, 'M', LT,   NONE,  ) /
 _VTE_REPLY(XTERM_FOCUS_OUT,                           CSI, 'O', NONE, NONE,  ) /* XTERM focus out report */
 _VTE_REPLY(DECXCPR,                                   CSI, 'R', WHAT, NONE,  ) /* extended cursor position 
report */
 _VTE_REPLY(CPR,                                       CSI, 'R', NONE, NONE,  ) /* cursor position report */
+_VTE_REPLY(XTERM_SMGRAPHICS_REPORT,                   CSI, 'S', WHAT, NONE,  ) /* xterm graphics attribute 
report */
 _VTE_REPLY(DECDA1R,                                   CSI, 'c', WHAT, NONE,  ) /* DA1 report */
 _VTE_REPLY(DECDA2R,                                   CSI, 'c', GT,   NONE,  ) /* DA2 report */
 _VTE_REPLY(SGR,                                       CSI, 'm', NONE, NONE,  ) /* SGR */
diff --git a/src/parser-seq.py b/src/parser-seq.py
index 2ed8314b..a349d1d9 100755
--- a/src/parser-seq.py
+++ b/src/parser-seq.py
@@ -547,8 +547,8 @@ sequences = [
             comment='scroll up'),
     seq_CSI('SPD', 'S', intermediates=(Intermediate.SPACE,),
             comment='select presentation directions'),
-    seq_CSI('XTERM_SGFX', 'S', pintro=(ParameterIntro.WHAT,), flags=Flags.NOP,
-            comment='xterm sixel graphics'),
+    seq_CSI('XTERM_SMGRAPHICS', 'S', pintro=(ParameterIntro.WHAT,),
+            comment='xterm graphics attributes'),
     seq_CSI('SD', 'T',
             comment='scroll down'),
     seq_CSI('XTERM_IHMT', 'T', flags=Flags.NOP,
diff --git a/src/sixel-context.hh b/src/sixel-context.hh
index 1754f8f5..8364702f 100644
--- a/src/sixel-context.hh
+++ b/src/sixel-context.hh
@@ -72,9 +72,9 @@ private:
         uint32_t m_introducer{0};
         uint32_t m_st{0};
 
-        static inline constexpr unsigned const k_max_width = 2048u;
+        static inline constexpr unsigned const k_max_width = VTE_SIXEL_MAX_WIDTH;
 
-        static inline constexpr unsigned const k_max_height = 2052u;
+        static inline constexpr unsigned const k_max_height = VTE_SIXEL_MAX_HEIGHT;
         static_assert((k_max_height % 6) == 0, "k_max_height not divisible by 6");
 
         static inline constexpr int const k_num_colors = VTE_SIXEL_NUM_COLOR_REGISTERS;
diff --git a/src/vtedefines.hh b/src/vtedefines.hh
index d3c07501..63150685 100644
--- a/src/vtedefines.hh
+++ b/src/vtedefines.hh
@@ -146,4 +146,6 @@
 
 #define VTE_SIXEL_ENABLED_DEFAULT false
 
+#define VTE_SIXEL_MAX_WIDTH (2048)
+#define VTE_SIXEL_MAX_HEIGHT (2052)
 #define VTE_SIXEL_NUM_COLOR_REGISTERS (1024)
diff --git a/src/vteseq.cc b/src/vteseq.cc
index 8a7a4906..461ef3c8 100644
--- a/src/vteseq.cc
+++ b/src/vteseq.cc
@@ -8724,13 +8724,124 @@ Terminal::XTERM_RTM(vte::parser::Sequence const& seq)
 }
 
 void
-Terminal::XTERM_SGFX(vte::parser::Sequence const& seq)
+Terminal::XTERM_SMGRAPHICS(vte::parser::Sequence const& seq)
 {
         /*
-         * XTERM_SGFX - xterm-sixel-graphics
+         * XTERM_SMGRAPHICS - xterm set or request graphics attributes
+         * Set or request graphics attributes for SIXEL and REGIS.
          *
-         * Probably not worth implementing.
+         * Reply: XTERM_SMGRAPHICS_REPORT
+         *
+         * Arguments:
+         *   args[0]: select function
+         *     0: number of colour registers
+         *     1: SIXEL geometry
+         *     2: REGIS geometry
+         *   args[1]: select subfunction
+         *     1: read attribute
+         *     2: reset attribute
+         *     3: set attribute
+         *     4: read maximum value of attribute
+         *   args[2:]: values, used only for subfuncion 3
+         *
+         * Defaults:
+         *   args[0]: no default
+         *   args[1]: no default
+         *   args[2:]: no default
+         *
+         * The reply is XTERM_SMGRAPHICS_REPORT, with arguments:
+         *   args[0]: function
+         *   args[1]: status
+         *     0: success
+         *     1: error in function parameter
+         *     2: error in subfunction parameter
+         *     3: failure
+         *
+         * References: XTERM
          */
+
+        auto const attr = seq.collect1(0);
+        auto const what = seq.collect1(1);
+        auto status = 3, rv0 = -2, rv1 = -2;
+
+        switch (attr) {
+#ifdef WITH_SIXEL
+        case 0: /* Colour registers.
+                 *
+                 * VTE doesn't support changing the number of colour registers, so always
+                 * return the fixed number, and set() returns success iff the passed number
+                 * was less or equal that number.
+                 */
+                switch (what) {
+                case 1: /* read */
+                case 2: /* reset */
+                case 4: /* read maximum */
+                        status = 0;
+                        rv0 = VTE_SIXEL_NUM_COLOR_REGISTERS;
+                        break;
+                case 3: /* set */
+                        status = (seq.collect1(2) <= VTE_SIXEL_NUM_COLOR_REGISTERS) ? 0 : 2;
+                        rv0 = VTE_SIXEL_NUM_COLOR_REGISTERS;
+                        break;
+                case -1: /* no default */
+                default:
+                        status = 2;
+                        break;
+                }
+                break;
+
+        case 1: /* SIXEL graphics geometry.
+                 *
+                 * VTE doesn't support variable geometries; always report
+                 * the maximum size of a SIXEL graphic, and set() returns success iff the
+                 * passed numbers are less or equal to that number.
+                 */
+                switch (what) {
+                case 1: /* read */
+                case 2: /* reset */
+                case 4: /* read maximum */
+                        status = 0;
+                        rv0 = VTE_SIXEL_MAX_WIDTH;
+                        rv1 = VTE_SIXEL_MAX_HEIGHT;
+                        break;
+
+                case 3: /* set */ {
+                        auto w = int{}, h = int{};
+                        if (seq.collect(2, {&w, &h}) &&
+                            w > 0 &&  w <= VTE_SIXEL_MAX_WIDTH &&
+                            h > 0 && h <= VTE_SIXEL_MAX_HEIGHT) {
+                                rv0 = VTE_SIXEL_MAX_WIDTH;
+                                rv1 = VTE_SIXEL_MAX_HEIGHT;
+                                status = 0;
+                        } else {
+                                status = 3;
+                        }
+
+                        break;
+                }
+
+                case -1: /* no default */
+                default:
+                        status = 2;
+                        break;
+                }
+                break;
+
+#endif /* WITH_SIXEL */
+
+#if 0 /* ifdef WITH_REGIS */
+        case 2:
+                status = 1;
+                break;
+#endif
+
+        case -1: /* no default value */
+        default:
+                status = 1;
+                break;
+        }
+
+        reply(seq, VTE_REPLY_XTERM_SMGRAPHICS_REPORT, {attr, status, rv0, rv1});
 }
 
 void