Change style of DAG generated in dag_drawer()

[emilkovacev]

Summary

Closes #13106

Adds non-breaking interface to dag_drawer() to allow Qiskit users to customize the colors of DAGs.

Details and comments

I created stylesheets for dag_drawer(), that works similarly to how circuit_drawer does.

Here is an example:

from qiskit import QuantumRegister, ClassicalRegister, QuantumCircuit
from qiskit.converters import circuit_to_dag
from qiskit.visualization import dag_drawer
 

q = QuantumRegister(3, 'q')
c = ClassicalRegister(3, 'c')
circ = QuantumCircuit(q, c)
circ.h(q[0])
circ.cx(q[0], q[1])
circ.measure(q[0], c[0])
circ.rz(0.5, q[1]).c_if(c, 2)

dag = circuit_to_dag(circ)

style = {
    # "fontsize": 12,
    # "bgcolor": "white",
    # "dpi": 10,
    # "pad": 0,
    # "nodecolor": "green",
    "inputnodecolor": "pink",
    # "inputnodefontcolor": "white",
    "outputnodecolor": "lightblue",
    # "outputnodefontcolor": "white",
    "opnodecolor": "red",
    # "opnodefontcolor": "white",
    # "edgecolor": "black",
    # "qubitedgecolor": "red",
    # "clbitedgecolor": "black",
}

dag_drawer(dag, style=style)

The code above generates this DAG:

[qiskit-bot]

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[coveralls]

Pull Request Test Coverage Report for Build 11308588283

Warning: This coverage report may be inaccurate.

This pull request's base commit is no longer the HEAD commit of its target branch. This means it includes changes from outside the original pull request, including, potentially, unrelated coverage changes.

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Details

• 18 of 167 (10.78%) changed or added relevant lines in 2 files are covered.
• 1133 unchanged lines in 38 files lost coverage.
• Overall coverage decreased (-0.3%) to 88.564%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
qiskit/visualization/dag/dagstyle.py	16	63	25.4%
qiskit/visualization/dag_visualization.py	2	104	1.92%

Files with Coverage Reduction	New Missed Lines	%
qiskit/transpiler/passes/optimization/elide_permutations.py	1	95.65%
qiskit/circuit/library/quantum_volume.py	1	97.3%
crates/accelerate/src/error_map.rs	1	85.42%
crates/accelerate/src/barrier_before_final_measurement.rs	2	97.33%
crates/circuit/src/lib.rs	2	96.15%
crates/circuit/src/bit_data.rs	2	94.62%
crates/accelerate/src/split_2q_unitaries.rs	2	96.0%
crates/accelerate/src/commutation_checker.rs	2	97.14%
crates/accelerate/src/check_map.rs	2	96.88%
qiskit/circuit/library/blueprintcircuit.py	4	96.4%

Totals
Change from base Build 11126578403:	-0.3%
Covered Lines:	73200
Relevant Lines:	82652

---

💛 - Coveralls

[mtreinish]

Thanks for getting this started. I left an inline comment about the high level interface. I'm a bit concerned with how low level the current interface is and that it would require understanding how graphviz is used internally by dag_drawer