From 812e27d36ffaf5d420c6572dcf656adbdaa329f3 Mon Sep 17 00:00:00 2001
From: Ivan Mahonin <bh@icystar.com>
Date: Jan 12 2021 12:31:29 +0000
Subject: fix strokes


---

diff --git a/src/drawing.c b/src/drawing.c
index e5d4fd0..517aa0c 100644
--- a/src/drawing.c
+++ b/src/drawing.c
@@ -658,7 +658,8 @@ static void drawStroke(int close) {
 	stroke.points = calloc(stroke.allocatedCount, sizeof(*stroke.points));
 	
 	double w = 0.5*s->strokeWidth;
-	double precisionSqr = 1/(w*0.75);
+  double ps = heliGLGetPixelSize();
+	double precisionSqr = ps > HELI_PRECISION ? ps : 0.5*w;
 	precisionSqr *= precisionSqr;
 	
 	heliDrawingApplyTexture(s->strokeColor, &s->strokeTexture);
diff --git a/src/geometry.c b/src/geometry.c
index 26b61fe..47d0e14 100644
--- a/src/geometry.c
+++ b/src/geometry.c
@@ -55,7 +55,7 @@ int heliMatrix4Invert(double *r, const double *m) {
 	r[12] = m[ 4]*(m[10]*m[13] - m[ 9]*m[14]) + m[ 5]*(m[ 8]*m[14] - m[10]*m[12]) + m[ 6]*(m[ 9]*m[12] - m[ 8]*m[13]);
 	
 	double det = m[ 0]*r[0] + m[ 1]*r[4] + m[ 2]*r[8] + m[ 3]*r[12];
-	if (fabs(det) <= HELI_PRECISION) {
+	if (fabs(det) <= HELI_PRECISION_SQR*HELI_PRECISION) {
 		memset(r, 0, sizeof(*r)*16);
 		return FALSE;
 	}
diff --git a/src/gl.c b/src/gl.c
index 98c95f2..821f2e9 100644
--- a/src/gl.c
+++ b/src/gl.c
@@ -60,6 +60,41 @@ double heliGLGetAAResolution() {
 }
 
 
+double heliGLGetPixelSize() {
+	double proj[16] = {};
+	double model[16] = {};
+	glGetDoublev(GL_PROJECTION_MATRIX, proj);
+	glGetDoublev(GL_MODELVIEW_MATRIX, model);
+	
+	double full[16] = {};
+	double fullinv[16] = {};
+	heliMatrix4Mult(full, proj, model);
+
+	full[8] = 0, full[9] = 0, full[10] = 1, full[11] = 0; // assume z is zero
+	if (!heliMatrix4Invert(fullinv, full)) return 0;
+	
+	if (fabs(fullinv[15]) <= HELI_PRECISION_SQR) return 0; // bad perspective
+	double k = 1/fullinv[15];
+	
+	if ( fabs(fullinv[3]*k) > 1e-5
+	  || fabs(fullinv[7]*k) > 1e-5 ) return 0; // perspective distortion
+	
+	int rect[4] = {}; // x, y, w, h
+	glGetIntegerv(GL_VIEWPORT, rect);
+	double w = rect[2], h = rect[3];
+	
+	double m00 = fullinv[0]*k*2/w, m01 = fullinv[1]*k*2/w,
+	       m10 = fullinv[4]*k*2/h, m11 = fullinv[5]*k*2/h;
+	double l0 = sqrt(m00*m00 + m01*m01);
+	double l1 = sqrt(m10*m10 + m11*m11);
+	if (l0 > l1) { double l = l0; l0 = l1; l1 = l; }
+	if (l0 <= HELI_PRECISION && l1 <= HELI_PRECISION) return 0;
+  
+  double l = sqrt(l0*l1);
+	return l <= HELI_PRECISION ? 0 : l;
+}
+
+
 static int isInteger(double x)
 	{ return fabs(floor(x + 0.5) - x) > 0.01; }
 
diff --git a/src/private.h b/src/private.h
index f95b701..79e8946 100644
--- a/src/private.h
+++ b/src/private.h
@@ -169,6 +169,7 @@ extern unsigned int heliGLWindowFramebufferReadId;
 extern unsigned int heliGLWindowFramebufferDrawId;
 
 double heliGLGetAAResolution();
+double heliGLGetPixelSize();
 int heliGLIsIntegerClipping();
 int heliGLBackTransform(double *x, double *y);
 void heliGLGetCommonState(HeliGLCommonState *state, unsigned int flags);