Skip to content

[graf2d] allow zero outer margins when dividing canvas #20209

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
wants to merge 2 commits into
base: master
Choose a base branch
from
+166 −29
Open

[graf2d] allow zero outer margins when dividing canvas #20209

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
9eb99eb
[graf2d] allow zero outer margins when dividing canvas
rlalik Oct 27, 2025
b948427
Redesign on TPad::Divide()
rlalik Nov 1, 2025
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
64 changes: 35 additions & 29 deletions graf2d/gpad/src/TPad.cxx
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -1254,6 +1254,9 @@ Int_t TPad::DistancetoPrimitive(Int_t px, Int_t py)
/// __Note3:__ in case xmargin < 0 or ymargin < 0, there is no space
/// between pads. The current pad margins are recomputed to
/// optimize the layout.
///
/// __Note4:__ in case nx < 0 or ny < 0, there is no outer x or y margin, but
/// the inner margins are equal to xmargin and ymargin, respectively.

void TPad::Divide(Int_t nx, Int_t ny, Float_t xmargin, Float_t ymargin, Int_t color)
{
Expand All @@ -1269,40 +1272,43 @@ void TPad::Divide(Int_t nx, Int_t ny, Float_t xmargin, Float_t ymargin, Int_t co
TContext ctxt(kTRUE);

cd();
if (nx <= 0) nx = 1;
if (ny <= 0) ny = 1;
Int_t ix, iy;
Double_t x1, y1, x2, y2, dx, dy;
TPad *pad;
if (nx == 0)
nx = 1;
if (ny == 0)
ny = 1;

Double_t xl = GetLeftMargin();
Double_t xr = GetRightMargin();
Double_t yb = GetBottomMargin();
Double_t yt = GetTopMargin();

TString name, title;
Int_t n = 0;
if (color == 0) color = GetFillColor();
if (xmargin >= 0 && ymargin >= 0) {
//general case
dy = 1/Double_t(ny);
dx = 1/Double_t(nx);
for (iy=0;iy<ny;iy++) {
y2 = 1 - iy*dy - ymargin;
y1 = y2 - dy + 2*ymargin;
if (y1 < 0) y1 = 0;
if (y1 > y2) continue;
for (ix=0;ix<nx;ix++) {
x1 = ix*dx + xmargin;
x2 = x1 +dx -2*xmargin;
if (x1 > x2) continue;
auto dx = (1 - xl - xr - xmargin * (nx - 1)) / nx; // width of a subpad
auto dy = (1 - yt - yb - ymargin * (ny - 1)) / ny; // height of a subpad

Int_t n = 0;
for (auto iy = 0; iy < ny; iy++) {
auto y2 = 1 - yt - iy * (dy + ymargin);
auto y1 = y2 - dy;
if (y1 < yb)
y1 = yb;
for (auto ix = 0; ix < nx; ix++) {
auto x1 = xl + ix * (dx + xmargin);
auto x2 = x1 + dx;
if (x2 > (1 - xr))
xr = 1 - xr;
n++;
name.Form("%s_%d", GetName(), n);
pad = new TPad(name.Data(), name.Data(), x1, y1, x2, y2, color);
auto pad = new TPad(name.Data(), name.Data(), x1, y1, x2, y2, color);
pad->SetNumber(n);
pad->Draw();
}
}
} else {
// special case when xmargin < 0 or ymargin < 0
Double_t xl = GetLeftMargin();
Double_t xr = GetRightMargin();
Double_t yb = GetBottomMargin();
Double_t yt = GetTopMargin();
xl /= (1-xl+xr)*nx;
xr /= (1-xl+xr)*nx;
yb /= (1-yb+yt)*ny;
Expand All @@ -1311,23 +1317,23 @@ void TPad::Divide(Int_t nx, Int_t ny, Float_t xmargin, Float_t ymargin, Int_t co
SetRightMargin(xr);
SetBottomMargin(yb);
SetTopMargin(yt);
dx = (1-xl-xr)/nx;
dy = (1-yb-yt)/ny;
auto dx = (1 - xl - xr) / nx;
auto dy = (1 - yb - yt) / ny;
Int_t number = 0;
for (Int_t i=0;i<nx;i++) {
x1 = i*dx+xl;
x2 = x1 + dx;
auto x1 = i * dx + xl;
auto x2 = x1 + dx;
if (i == 0) x1 = 0;
if (i == nx-1) x2 = 1-xr;
for (Int_t j=0;j<ny;j++) {
number = j*nx + i +1;
y2 = 1 -j*dy -yt;
y1 = y2 - dy;
auto y2 = 1 - j * dy - yt;
auto y1 = y2 - dy;
if (j == 0) y2 = 1-yt;
if (j == ny-1) y1 = 0;
name.Form("%s_%d", GetName(), number);
title.Form("%s_%d", GetTitle(), number);
pad = new TPad(name.Data(), title.Data(), x1, y1, x2, y2, color);
auto pad = new TPad(name.Data(), title.Data(), x1, y1, x2, y2, color);
pad->SetNumber(number);
pad->SetBorderMode(0);
if (i == 0) pad->SetLeftMargin(xl*nx);
Expand Down
131 changes: 131 additions & 0 deletions tutorials/visualisation/graphics/canvas_divide_example.C
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -0,0 +1,131 @@
// variants: 0 - custom values
// 1 - default values
// 2+ - old default values
void canvas_divide_example(int use_variant = 0)
{
auto wx = 600; // width and heigh
auto wy = 400;

auto nx = 3; // top-level pad division
auto ny = 2;

auto ml = 0.30; // top-level pad margins
auto mb = 0.10;
auto mr = 0.05;
auto mt = 0.10;

auto c = new TCanvas("canvas_divide", "canvas_divide", wx, wy);
c->SetFillColor(19);

if (use_variant == 0) {
c->SetLeftMargin(ml);
c->SetBottomMargin(mb);
c->SetRightMargin(mr);
c->SetTopMargin(mt);

c->Divide(nx, ny, 0.03, 0.05, 46);
} else if (use_variant == 1) {
c->Divide(nx, ny, 0.01, 0.01, 46);
} else {
c->SetLeftMargin(0.01);
c->SetBottomMargin(0.01);
c->SetRightMargin(0.01);
c->SetTopMargin(0.01);

c->Divide(nx, ny, 0.02, 0.02, 46);
}

ml = c->GetLeftMargin();
mb = c->GetBottomMargin();
mr = c->GetRightMargin();
mt = c->GetTopMargin();

auto h = new TH1F("", "", 100, -3.3, 3.3);
h->GetXaxis()->SetLabelFont(43);
h->GetXaxis()->SetLabelSize(12);
h->GetYaxis()->SetLabelFont(43);
h->GetYaxis()->SetLabelSize(12);
h->GetYaxis()->SetNdivisions(505);
h->SetMaximum(30 * nx * ny);
h->SetFillColor(41);

Int_t number = 0;
for (Int_t i = 0; i < nx * ny; i++) {
number++;
c->cd(number);
h->FillRandom("gaus", 1000);
h->DrawCopy();
}

c->cd();

TArrow arr;

arr.DrawArrow(0, 0.5, ml, 0.5, 0.01, "<|>");
arr.DrawArrow(0.5, 0, 0.5, mb, 0.01, "<|>");
arr.DrawArrow(1 - mr, 0.5, 1, 0.5, 0.01, "<|>");
arr.DrawArrow(0.5, 1 - mt, 0.5, 1, 0.01, "<|>");

TLatex tex_x;
tex_x.SetNDC(1);
tex_x.SetTextSize(0.03);
tex_x.SetTextAlign(12);
tex_x.SetTextAngle(90);

TLatex tex_y;
tex_y.SetNDC(1);
tex_y.SetTextSize(0.03);
tex_y.SetTextAlign(12);

tex_x.DrawLatex(ml / 2, 0.5, TString::Format(" ml = %.2f", ml));
tex_x.DrawLatex(1 - mr / 2, 0.5, TString::Format(" mr = %.2f", mr));

tex_y.DrawLatex(0.5, mb / 2, TString::Format(" mb = %.2f", mb));
tex_y.DrawLatex(0.5, 1 - mt / 2, TString::Format(" mt = %.2f", mt));

for (int i = 0; i < nx; ++i) {
for (int j = 0; j < ny; ++j) {

float x1, x2, xc, y1, y2, yc;

auto spad = c->GetPad(1 + j * nx + i); // current pad
x1 = spad->GetXlowNDC() + spad->GetWNDC();
xc = spad->GetXlowNDC() + spad->GetWNDC() / 2;
if (i < (nx - 1)) {
auto spad_nx = c->GetPad(1 + j * nx + (i + 1)); // next pad in x
x2 = spad_nx->GetXlowNDC();
}
auto xm = x2 - x1;

if (j < (ny - 1)) {
auto spad_ny = c->GetPad(1 + (j + 1) * nx + i); // next pad in y
y1 = spad_ny->GetYlowNDC() + spad->GetHNDC();
}
y2 = spad->GetYlowNDC();
yc = spad->GetYlowNDC() + spad->GetHNDC() / 2;
auto ym = y2 - y1;

if (i < (nx - 1)) {
arr.DrawArrow(x1, yc, x2, yc, 0.01, "<|>");
tex_x.DrawLatex((x1 + x2) / 2, yc, TString::Format(" xm = %.2f", xm));
}
if (j < (ny - 1)) {
arr.DrawArrow(xc, y1, xc, y2, 0.01, "<|>");
tex_y.DrawLatex(xc, (y1 + y2) / 2, TString::Format(" ym = %.2f", ym));
}
}
}

TText text;
text.SetTextSize(0.03);
text.SetTextFont(102);
text.SetNDC(1);

if (use_variant == 0) {
text.DrawText(0.01, 0.90, "c->SetLeftMargin(ml);");
text.DrawText(0.01, 0.85, "c->SetBottomMargin(mb);");
text.DrawText(0.01, 0.80, "c->SetRightMargin(mr);");
text.DrawText(0.01, 0.75, "c->SetTopMargin(mt);");
text.DrawText(0.01, 0.70, "c->Divide(nx, ny, xm, ym);");
}
}