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cleanup canvas piano roll header so that it can exist with no current MidiView

This commit is contained in:
Paul Davis 2024-02-09 20:59:50 -07:00
parent d356cacb2a
commit 59ed3d7138
7 changed files with 184 additions and 137 deletions

View File

@ -42,6 +42,8 @@ CueMidiBackground::set_size (double w, double h)
_height = h;
update_contents_height ();
HeightChanged (); /* EMIT SIGNAL */
}
double

View File

@ -188,6 +188,15 @@ MidiCueEditor::build_canvas ()
bg = new CueMidiBackground (data_group);
_canvas_viewport->signal_size_allocate().connect (sigc::mem_fun(*this, &MidiCueEditor::canvas_allocate));
prh = new ArdourCanvas::PianoRollHeader (v_scroll_group, *bg);
double w, h;
prh->size_request (w, h);
prh->set_position (Duple (0., n_timebars * timebar_height));
data_group->set_position (ArdourCanvas::Duple (w, timebar_height * n_timebars));
h_scroll_group->set_position (Duple (w, 0.));
_canvas->set_name ("MidiCueCanvas");
_canvas->add_events (Gdk::POINTER_MOTION_HINT_MASK | Gdk::SCROLL_MASK | Gdk::KEY_PRESS_MASK | Gdk::KEY_RELEASE_MASK);
_canvas->set_can_focus ();
@ -317,18 +326,16 @@ MidiCueEditor::set_region (std::shared_ptr<ARDOUR::MidiTrack> t, std::shared_ptr
view->set_region (r);
bg->set_view (view);
delete prh;
prh = new ArdourCanvas::PianoRollHeader (v_scroll_group, *view);
prh->set_view (*view);
double w, h;
prh->size_request (w, h);
/* Move stuff around */
prh->move (Duple (0., n_timebars * timebar_height));
data_group->move (ArdourCanvas::Duple (w, timebar_height * n_timebars));
h_scroll_group->move (Duple (w, 0.));
prh->set_position (Duple (0., n_timebars * timebar_height));
data_group->set_position (ArdourCanvas::Duple (w, timebar_height * n_timebars));
h_scroll_group->set_position (Duple (w, 0.));
/* Compute zoom level to show entire source plus some margin if possible */

View File

@ -52,6 +52,8 @@ MidiViewBackground::MidiViewBackground (ArdourCanvas::Item* parent)
note_range_adjustment.set_page_size(_highest_note - _lowest_note);
note_range_adjustment.set_value(_lowest_note);
note_range_adjustment.set_lower(0);
note_range_adjustment.set_upper(127);
note_range_adjustment.signal_value_changed().connect(sigc::mem_fun(*this, &MidiViewBackground::note_range_adjustment_changed));
}

View File

@ -27,6 +27,8 @@
#include <gtkmm/adjustment.h>
#include "pbd/signals.h"
#include "ardour/types.h"
#include "gtkmm2ext/colors.h"
@ -97,6 +99,9 @@ class MidiViewBackground : public virtual ViewBackground
virtual void set_note_highlight (bool) = 0;
virtual void record_layer_check (std::shared_ptr<ARDOUR::Region>, samplepos_t) = 0;
virtual void set_size (double w, double h) {}
PBD::Signal0<void> HeightChanged;
protected:
bool _range_dirty;
double _range_sum_cache;

View File

@ -31,13 +31,15 @@
#include "gtkmm2ext/keyboard.h"
#include "gtkmm2ext/rgb_macros.h"
#include "midi++/midnam_patch.h"
#include "editing.h"
#include "gui_thread.h"
#include "midi_view.h"
#include "midi_view_background.h"
#include "prh.h"
#include "editing_context.h"
#include "ui_config.h"
#include "midi++/midnam_patch.h"
#include "pbd/i18n.h"
@ -46,11 +48,11 @@ using namespace Gtkmm2ext;
namespace ArdourCanvas {
PianoRollHeader::PianoRollHeader (Item* parent, MidiView& v)
PianoRollHeader::PianoRollHeader (Item* parent, MidiViewBackground& bg)
: Rectangle (parent)
, have_note_names (false)
, _adj (v.midi_context().note_range_adjustment)
, _view (v)
, _midi_context (bg)
, _adj (_midi_context.note_range_adjustment)
, _view (nullptr)
, _font_descript ("Sans Bold")
, _font_descript_big_c ("Sans")
, _font_descript_midnam ("Sans")
@ -67,6 +69,7 @@ PianoRollHeader::PianoRollHeader (Item* parent, MidiView& v)
, _saved_bottom_val (127.0)
, _mini_map_display (false)
, entered (false)
, have_note_names (false)
{
Glib::RefPtr<Pango::Context> context = _canvas->get_pango_context();
@ -76,26 +79,16 @@ PianoRollHeader::PianoRollHeader (Item* parent, MidiView& v)
_big_c_layout->set_font_description(_font_descript_big_c);
_midnam_layout = Pango::Layout::create (context);
_adj.set_lower(0);
_adj.set_upper(127);
/* set minimum view range to one octave */
//set_min_page_size(12);
//_adj = v->note_range_adjustment;
for (int i = 0; i < 128; ++i) {
_active_notes[i] = false;
}
_view.midi_context().NoteRangeChanged.connect (sigc::mem_fun (*this, &PianoRollHeader::note_range_changed));
double w, h;
size_request (w, h);
set (Rect (0., 0., w, h));
resize ();
bg.HeightChanged.connect (height_connection, MISSING_INVALIDATOR, boost::bind (&PianoRollHeader::resize, this), gui_context());
/* draw vertical lines on both sides of the rectangle */
set_fill (false);
set_fill (true);
set_outline_color (0x000000ff); /* XXX theme me */
set_outline_what (Rectangle::What (Rectangle::LEFT|Rectangle::RIGHT));
@ -103,23 +96,32 @@ PianoRollHeader::PianoRollHeader (Item* parent, MidiView& v)
}
void
PianoRollHeader::size_request (double& w, double& h) const
PianoRollHeader::resize ()
{
h = _view.midi_context().contents_height();
if (show_scroomer()) {
w = 60.f * UIConfiguration::instance().get_ui_scale();
} else {
w = 20.f * UIConfiguration::instance().get_ui_scale();
}
w += 20.;
double w, h;
size_request (w, h);
set (Rect (0., 0., w, h));
}
void
PianoRollHeader::size_allocate (ArdourCanvas::Rect const &r)
PianoRollHeader::set_view (MidiView& v)
{
_alloc = r;
_view = &v;
_view->midi_context().NoteRangeChanged.connect (sigc::mem_fun (*this, &PianoRollHeader::note_range_changed));
}
void
PianoRollHeader::size_request (double& w, double& h) const
{
h = _midi_context.contents_height();
if (show_scroomer()) {
_scroomer_size = 60.f * UIConfiguration::instance().get_ui_scale();
} else {
_scroomer_size = 20.f * UIConfiguration::instance().get_ui_scale();
}
w = _scroomer_size + 20.;
}
bool
@ -212,16 +214,20 @@ PianoRollHeader::render_scroomer(Cairo::RefPtr<Cairo::Context> cr) const
bool
PianoRollHeader::scroll_handler (GdkEventScroll* ev)
{
if (!_view) {
return false;
}
int note_range = _adj.get_page_size ();
int note_lower = _adj.get_value ();
if(ev->state == GDK_SHIFT_MASK){
switch (ev->direction) {
case GDK_SCROLL_UP: //ZOOM IN
_view.apply_note_range (min(note_lower + 1, 127), max(note_lower + note_range - 1,0), true);
_view->apply_note_range (min(note_lower + 1, 127), max(note_lower + note_range - 1,0), true);
break;
case GDK_SCROLL_DOWN: //ZOOM OUT
_view.apply_note_range (max(note_lower - 1,0), min(note_lower + note_range + 1, 127), true);
_view->apply_note_range (max(note_lower - 1,0), min(note_lower + note_range + 1, 127), true);
break;
default:
return false;
@ -240,7 +246,7 @@ PianoRollHeader::scroll_handler (GdkEventScroll* ev)
}
Duple evd (canvas_to_item (Duple (ev->x, ev->y)));
set_note_highlight (_view.midi_context().y_to_note (evd.y));
set_note_highlight (_view->midi_context().y_to_note (evd.y));
_adj.value_changed ();
redraw ();
@ -251,14 +257,14 @@ PianoRollHeader::scroll_handler (GdkEventScroll* ev)
void
PianoRollHeader::get_path (int note, double x[], double y[]) const
{
double y_pos = floor(_view.midi_context().note_to_y(note));
double y_pos = floor(_midi_context.note_to_y(note));
double note_height;
double width = get().width() - 1.0f;
if (note == 0) {
note_height = floor(_view.midi_context().contents_height()) - y_pos;
note_height = floor(_midi_context.contents_height()) - y_pos;
} else {
note_height = _view.midi_context().note_height() <= 3 ? _view.midi_context().note_height() : _view.midi_context().note_height() - 1.f;
note_height = _midi_context.note_height() <= 3 ? _midi_context.note_height() : _midi_context.note_height() - 1.f;
}
x[0] = _scroomer_size;
@ -288,6 +294,10 @@ PianoRollHeader::render (ArdourCanvas::Rect const & area, Cairo::RefPtr<Cairo::C
Rectangle::render (area, cr);
/* Setup a cairo translation so that all drawing can be done using item
* coordinate
*/
Duple origin (item_to_window (Duple (0., 0.)));
cr->save ();
@ -296,8 +306,8 @@ PianoRollHeader::render (ArdourCanvas::Rect const & area, Cairo::RefPtr<Cairo::C
Rect self (get());
double y1 = max (self.y0, 0.);
double y2 = min (self.y1, (ArdourCanvas::Coord) floor(_view.midi_context().contents_height()));
double av_note_height = _view.midi_context().note_height();
double y2 = min (self.y1, (ArdourCanvas::Coord) floor(_midi_context.contents_height()));
double av_note_height = _midi_context.note_height();
int bc_height, bc_width;
//Reduce the frequency of Pango layout resizing
@ -318,8 +328,8 @@ PianoRollHeader::render (ArdourCanvas::Rect const & area, Cairo::RefPtr<Cairo::C
_midnam_layout->set_font_description(_font_descript_midnam);
lowest = max(_view.midi_context().lowest_note(), _view.midi_context().y_to_note(y2));
highest = min(_view.midi_context().highest_note(), _view.midi_context().y_to_note(y1));
lowest = max(_midi_context.lowest_note(), _midi_context.y_to_note(y2));
highest = min(_midi_context.highest_note(), _midi_context.y_to_note(y1));
if (lowest > 127) {
lowest = 0;
@ -355,7 +365,7 @@ PianoRollHeader::render (ArdourCanvas::Rect const & area, Cairo::RefPtr<Cairo::C
for (int i = lowest; i <= highest; ++i) {
int size_x, size_y;
double y = floor(_view.midi_context().note_to_y(i)) - 0.5f;
double y = floor(_midi_context.note_to_y(i)) - 0.5f;
NoteName const & note (note_names[i]);
_midnam_layout->set_text (note.name);
@ -466,8 +476,8 @@ PianoRollHeader::render (ArdourCanvas::Rect const & area, Cairo::RefPtr<Cairo::C
so that the top of the C is shown to maintain visual context
*/
for (int i = lowest - 5; i <= highest; ++i) {
double y = floor(_view.midi_context().note_to_y(i)) - 0.5f;
double note_height = i == 0? av_note_height : floor(_view.midi_context().note_to_y(i - 1)) - y;
double y = floor(_midi_context.note_to_y(i)) - 0.5f;
double note_height = i == 0? av_note_height : floor(_midi_context.note_to_y(i - 1)) - y;
oct_rel = i % 12;
if (oct_rel == 0 || (oct_rel == 7 && _adj.get_page_size() <=10)) {
@ -476,9 +486,9 @@ PianoRollHeader::render (ArdourCanvas::Rect const & area, Cairo::RefPtr<Cairo::C
int cn = i / 12 - 1;
if (oct_rel == 0){
s << "C" << cn;
s << 'C' << cn;
} else {
s << "G" << cn;
s << 'G' << cn;
}
if (av_note_height > 12.0){
@ -523,8 +533,9 @@ PianoRollHeader::instrument_info_change ()
width.
*/
_view.midi_track()->gui_changed ("visible_tracks", (void *) 0); /* EMIT SIGNAL */
if (_view) {
_view->midi_track()->gui_changed ("visible_tracks", (void *) 0); /* EMIT SIGNAL */
}
}
@ -609,28 +620,34 @@ PianoRollHeader::get_note_name (int note)
bool
PianoRollHeader::motion_handler (GdkEventMotion* ev)
{
if (!_view) {
return false;
}
Duple evd (canvas_to_item (Duple (ev->x, ev->y)));
if (!_scroomer_drag && ev->x < _scroomer_size){
Gdk::Cursor m_Cursor;
double scroomer_top = max(1.0, (1.0 - ((_adj.get_value()+_adj.get_page_size()) / 127.0)) * get().height());
double scroomer_bottom = (1.0 - (_adj.get_value () / 127.0)) * get().height();
if (evd.y > scroomer_top - 5 && evd.y < scroomer_top + 5){
m_Cursor = Gdk::Cursor (Gdk::TOP_SIDE);
_view.editing_context().push_canvas_cursor (&m_Cursor);
_view->editing_context().push_canvas_cursor (&m_Cursor);
_scroomer_state = TOP;
} else if (evd.y > scroomer_bottom - 5 && evd.y < scroomer_bottom + 5){
m_Cursor = Gdk::Cursor (Gdk::BOTTOM_SIDE);
_view.editing_context().push_canvas_cursor (&m_Cursor);
_view->editing_context().push_canvas_cursor (&m_Cursor);
_scroomer_state = BOTTOM;
} else {
_scroomer_state = MOVE;
_view.editing_context().pop_canvas_cursor ();
_view->editing_context().pop_canvas_cursor ();
}
}
if (_scroomer_drag){
double pixel2val = 127.0 / get().height();
double delta = _old_y - evd.y;
double val_at_pointer = (delta * pixel2val);
@ -647,30 +664,32 @@ PianoRollHeader::motion_handler (GdkEventMotion* ev)
case TOP:
real_val_at_pointer = real_val_at_pointer <= _saved_top_val? _adj.get_value() + _adj.get_page_size() : real_val_at_pointer;
real_val_at_pointer = min(127.0, real_val_at_pointer);
if (_view.midi_context().note_height() >= UIConfiguration::instance().get_max_note_height()){
if (_midi_context.note_height() >= UIConfiguration::instance().get_max_note_height()){
_saved_top_val = min(_adj.get_value() + _adj.get_page_size (), 127.0);
} else {
_saved_top_val = 0.0;
}
//if we are at largest note size & the user is moving down don't do anything
//FIXME we are using a heuristic of 18.5 for max note size, but this changes when track size is small to 19.5?
_view.midi_context().apply_note_range (_adj.get_value (), real_val_at_pointer, true);
_midi_context.apply_note_range (_adj.get_value (), real_val_at_pointer, true);
break;
case BOTTOM:
real_val_at_pointer = max(0.0, real_val_at_pointer);
real_val_at_pointer = real_val_at_pointer >= _saved_bottom_val? _adj.get_value() : real_val_at_pointer;
if (_view.midi_context().note_height() >= UIConfiguration::instance().get_max_note_height()){
if (_midi_context.note_height() >= UIConfiguration::instance().get_max_note_height()){
_saved_bottom_val = _adj.get_value();
} else {
_saved_bottom_val = 127.0;
}
_view.midi_context().apply_note_range (real_val_at_pointer, _adj.get_value () + _adj.get_page_size (), true);
_midi_context.apply_note_range (real_val_at_pointer, _adj.get_value () + _adj.get_page_size (), true);
break;
default:
break;
}
} else {
int note = _view.midi_context().y_to_note(evd.y);
int note = _midi_context.y_to_note(evd.y);
set_note_highlight (note);
if (_dragging) {
@ -700,7 +719,7 @@ PianoRollHeader::motion_handler (GdkEventMotion* ev)
}
}
}
_adj.value_changed ();
redraw ();
_old_y = evd.y;
//win->process_updates(false);
@ -711,6 +730,10 @@ PianoRollHeader::motion_handler (GdkEventMotion* ev)
bool
PianoRollHeader::button_press_handler (GdkEventButton* ev)
{
if (!_view) {
return false;
}
/* Convert canvas-coordinates to item coordinates */
Duple evd (canvas_to_item (Duple (ev->x, ev->y)));
@ -719,7 +742,7 @@ PianoRollHeader::button_press_handler (GdkEventButton* ev)
if (ev->button == 1 && ev->x <= _scroomer_size){
if (ev->type == GDK_2BUTTON_PRESS) {
_view.set_visibility_note_range (MidiStreamView::ContentsRange, false);
_view->set_visibility_note_range (MidiStreamView::ContentsRange, false);
return true;
}
@ -730,7 +753,7 @@ PianoRollHeader::button_press_handler (GdkEventButton* ev)
return true;
} else {
int note = _view.midi_context().y_to_note(evd.y);
int note = _midi_context.y_to_note(evd.y);
bool tertiary = Keyboard::modifier_state_contains (ev->state, Keyboard::TertiaryModifier);
bool primary = Keyboard::modifier_state_contains (ev->state, Keyboard::PrimaryModifier);
@ -777,7 +800,7 @@ PianoRollHeader::button_release_handler (GdkEventButton* ev)
_scroomer_drag = false;
int note = _view.midi_context().y_to_note(evd.y);
int note = _midi_context.y_to_note(evd.y);
if (false /*editor().current_mouse_mode() == Editing::MouseRange*/) { //Todo: this mode is buggy, and of questionable utility anyway
@ -829,7 +852,7 @@ bool
PianoRollHeader::enter_handler (GdkEventCrossing* ev)
{
Duple evd (canvas_to_item (Duple (ev->x, ev->y)));
set_note_highlight (_view.midi_context().y_to_note (evd.y));
set_note_highlight (_midi_context.y_to_note (evd.y));
entered = true;
redraw ();
return true;
@ -839,7 +862,9 @@ bool
PianoRollHeader::leave_handler (GdkEventCrossing*)
{
if (!_scroomer_drag){
_view.editing_context().pop_canvas_cursor ();
if (_view) {
_view->editing_context().pop_canvas_cursor ();
}
}
invalidate_note_range(_highlighted_note, _highlighted_note);
@ -863,11 +888,11 @@ PianoRollHeader::note_range_changed ()
void
PianoRollHeader::invalidate_note_range (int lowest, int highest)
{
lowest = max((int) _view.midi_context().lowest_note(), lowest - 1);
highest = min((int) _view.midi_context().highest_note(), highest + 2);
lowest = max((int) _midi_context.lowest_note(), lowest - 1);
highest = min((int) _midi_context.highest_note(), highest + 2);
double y = _view.midi_context().note_to_y (highest);
double height = _view.midi_context().note_to_y (lowest - 1) - y;
double y = _midi_context.note_to_y (highest);
double height = _midi_context.note_to_y (lowest - 1) - y;
dynamic_cast<ArdourCanvas::GtkCanvas*>(_canvas)->queue_draw_area (0., floor (y), get().width(), floor (height));
}
@ -875,13 +900,17 @@ PianoRollHeader::invalidate_note_range (int lowest, int highest)
bool
PianoRollHeader::show_scroomer () const
{
if (!_view) {
return false;
}
Editing::NoteNameDisplay nnd = UIConfiguration::instance().get_note_name_display();
if (nnd == Editing::Never) {
return false;
}
switch (_view.editing_context().current_mouse_mode()) {
switch (_view->editing_context().current_mouse_mode()) {
case Editing::MouseDraw:
case Editing::MouseContent:
if (nnd == Editing::WithMIDNAM) {
@ -898,12 +927,16 @@ PianoRollHeader::show_scroomer () const
void
PianoRollHeader::send_note_on (uint8_t note)
{
std::shared_ptr<ARDOUR::MidiTrack> track = _view.midi_track ();
if (!_view) {
return;
}
std::shared_ptr<ARDOUR::MidiTrack> track = _view->midi_track ();
//cerr << "note on: " << (int) note << endl;
if (track) {
_event[0] = (MIDI_CMD_NOTE_ON | _view.midi_context().get_preferred_midi_channel ());
_event[0] = (MIDI_CMD_NOTE_ON | _midi_context.get_preferred_midi_channel ());
_event[1] = note;
_event[2] = 100;
@ -914,10 +947,14 @@ PianoRollHeader::send_note_on (uint8_t note)
void
PianoRollHeader::send_note_off (uint8_t note)
{
std::shared_ptr<ARDOUR::MidiTrack> track = _view.midi_track ();
if (!_view) {
return;
}
std::shared_ptr<ARDOUR::MidiTrack> track = _view->midi_track ();
if (track) {
_event[0] = (MIDI_CMD_NOTE_OFF | _view.midi_context().get_preferred_midi_channel ());
_event[0] = (MIDI_CMD_NOTE_OFF | _midi_context.get_preferred_midi_channel ());
_event[1] = note;
_event[2] = 100;

View File

@ -39,12 +39,10 @@ namespace ArdourCanvas {
class PianoRollHeader : public ArdourCanvas::Rectangle {
public:
PianoRollHeader (ArdourCanvas::Item* parent, MidiView&);
PianoRollHeader (ArdourCanvas::Item* parent, MidiViewBackground&);
void size_request (double& w, double& h) const;
void render (ArdourCanvas::Rect const & area, Cairo::RefPtr<Cairo::Context>) const;
void size_allocate (ArdourCanvas::Rect const &);
void instrument_info_change ();
@ -56,53 +54,12 @@ public:
sigc::signal<void,uint8_t> ToggleNoteSelection;
sigc::signal<void,uint8_t> ExtendNoteSelection;
void set_view (MidiView&);
private:
bool event_handler (GdkEvent*);
bool motion_handler (GdkEventMotion*);
bool button_press_handler (GdkEventButton*);
bool button_release_handler (GdkEventButton*);
bool scroll_handler (GdkEventScroll*);
bool enter_handler (GdkEventCrossing*);
bool leave_handler (GdkEventCrossing*);
// void on_size_request(Gtk::Requisition*);
struct NoteName {
std::string name;
bool from_midnam;
};
NoteName note_names[128];
bool have_note_names;
void set_min_page_size(double page_size);
void render_scroomer(Cairo::RefPtr<Cairo::Context>) const;
NoteName get_note_name (int note);
MidiViewBackground& _midi_context;
Gtk::Adjustment& _adj;
PianoRollHeader(const PianoRollHeader&);
enum ItemType {
BLACK_SEPARATOR,
BLACK_MIDDLE_SEPARATOR,
BLACK,
WHITE_SEPARATOR,
WHITE_RECT,
WHITE_CF,
WHITE_EB,
WHITE_DGA
};
void invalidate_note_range(int lowest, int highest);
void get_path(int note, double x[], double y[]) const;
void send_note_on(uint8_t note);
void send_note_off(uint8_t note);
void reset_clicked_note(uint8_t, bool invalidate = true);
MidiView& _view;
MidiView* _view;
uint8_t _event[3];
@ -117,7 +74,7 @@ private:
uint8_t _clicked_note;
double _grab_y;
bool _dragging;
double _scroomer_size;
mutable double _scroomer_size;
bool _scroomer_drag;
double _old_y;
double _fract;
@ -131,9 +88,46 @@ private:
mutable bool _mini_map_display;
bool entered;
bool show_scroomer () const;
// void on_size_request(Gtk::Requisition*);
ArdourCanvas::Rect _alloc;
struct NoteName {
std::string name;
bool from_midnam;
};
NoteName note_names[128];
bool have_note_names;
PBD::ScopedConnection height_connection;
void set_min_page_size (double page_size);
void render_scroomer (Cairo::RefPtr<Cairo::Context>) const;
NoteName get_note_name (int note);
bool event_handler (GdkEvent*);
bool motion_handler (GdkEventMotion*);
bool button_press_handler (GdkEventButton*);
bool button_release_handler (GdkEventButton*);
bool scroll_handler (GdkEventScroll*);
bool enter_handler (GdkEventCrossing*);
bool leave_handler (GdkEventCrossing*);
enum ItemType {
BLACK_SEPARATOR,
BLACK_MIDDLE_SEPARATOR,
BLACK,
WHITE_SEPARATOR,
WHITE_RECT,
WHITE_CF,
WHITE_EB,
WHITE_DGA
};
void invalidate_note_range (int lowest, int highest);
void get_path (int note, double x[], double y[]) const;
void send_note_on (uint8_t note);
void send_note_off (uint8_t note);
void reset_clicked_note (uint8_t, bool invalidate = true);
bool show_scroomer () const;
void resize ();
};
}

View File

@ -111,7 +111,7 @@ Ruler::set_second_font_description (Pango::FontDescription fd)
void
Ruler::render (Rect const & area, Cairo::RefPtr<Cairo::Context> cr) const
{
std::cerr << whoami() << " ruler render " << _lower << " .. " << _upper << "\n";
// std::cerr << whoami() << " ruler render " << _lower << " .. " << _upper << "\n";
if (_lower == _upper) {
/* nothing to draw */